diff --git a/backend/internal/service/hydra_admin_service_test.go b/backend/internal/service/hydra_admin_service_test.go
new file mode 100644
index 00000000..0004e590
--- /dev/null
+++ b/backend/internal/service/hydra_admin_service_test.go
@@ -0,0 +1,401 @@
+/*
+이 테스트 파일은 HydraAdminService의 기능을 검증하기 위한 유닛 테스트입니다.
+Hydra Admin API와의 통신을 시뮬레이션하기 위해 httptest 패키지를 사용하여
+실제 네트워크 호출 없이 HTTP 핸들러를 모킹(Mocking)하는 방식으로 작성되었습니다.
+
+주요 테스트 항목:
+1. 클라이언트 관리: List, Get, Create, Update, Patch, Delete (성공 및 NotFound 케이스)
+2. OIDC 인증/동의 흐름: GetConsentRequest, AcceptConsentRequest, RejectConsentRequest, GetLoginRequest, AcceptLoginRequest, RejectLoginRequest
+3. 세션 관리: ListConsentSessions, RevokeConsentSessions
+4. 존재하지 않는 리소스 접근 시 에러 처리
+*/
+
+package service
+
+import (
+	"baron-sso-backend/internal/domain"
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// clientForHandler는 주어진 핸들러로 요청을 보내는 http.Client를 반환합니다.
+// ory_service_test.go에 정의된 것과 동일한 로직입니다.
+func mockHydraClient(h http.Handler) *http.Client {
+	return &http.Client{
+		Transport: roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+			var bodyBytes []byte
+			if req.Body != nil {
+				bodyBytes, _ = io.ReadAll(req.Body)
+			}
+			r := httptest.NewRequest(req.Method, req.URL.String(), bytes.NewReader(bodyBytes))
+			r.Header = req.Header.Clone()
+
+			w := httptest.NewRecorder()
+			h.ServeHTTP(w, r)
+			return w.Result(), nil
+		}),
+	}
+}
+
+func TestHydraAdminService_ListClients(t *testing.T) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet || !strings.Contains(r.URL.Path, "/clients") {
+			t.Errorf("unexpected request: %s %s", r.Method, r.URL.String())
+			return
+		}
+
+		clients := []domain.HydraClient{
+			{ClientID: "client-1", ClientName: "Client One"},
+			{ClientID: "client-2", ClientName: "Client Two"},
+		}
+		json.NewEncoder(w).Encode(clients)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	clients, err := svc.ListClients(context.Background(), 10, 0)
+	if err != nil {
+		t.Fatalf("ListClients failed: %v", err)
+	}
+
+	if len(clients) != 2 {
+		t.Errorf("expected 2 clients, got %d", len(clients))
+	}
+}
+
+func TestHydraAdminService_GetClient_Success(t *testing.T) {
+	targetID := "test-client"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		client := domain.HydraClient{
+			ClientID:   targetID,
+			ClientName: "Test Client",
+		}
+		json.NewEncoder(w).Encode(client)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	client, err := svc.GetClient(context.Background(), targetID)
+	if err != nil {
+		t.Fatalf("GetClient failed: %v", err)
+	}
+
+	if client.ClientID != targetID {
+		t.Errorf("expected %s, got %s", targetID, client.ClientID)
+	}
+}
+
+func TestHydraAdminService_GetClient_NotFound(t *testing.T) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	_, err := svc.GetClient(context.Background(), "non-existent")
+	if err != ErrHydraNotFound {
+		t.Errorf("expected ErrHydraNotFound, got %v", err)
+	}
+}
+
+func TestHydraAdminService_PatchClientStatus(t *testing.T) {
+	targetID := "test-client"
+	status := "inactive"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPatch {
+			t.Errorf("expected PATCH, got %s", r.Method)
+		}
+		var patch []map[string]interface{}
+		json.NewDecoder(r.Body).Decode(&patch)
+		if patch[0]["value"] != status {
+			t.Errorf("expected status %s, got %v", status, patch[0]["value"])
+		}
+
+		client := domain.HydraClient{ClientID: targetID}
+		json.NewEncoder(w).Encode(client)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	_, err := svc.PatchClientStatus(context.Background(), targetID, status)
+	if err != nil {
+		t.Fatalf("PatchClientStatus failed: %v", err)
+	}
+}
+
+func TestHydraAdminService_CreateClient(t *testing.T) {
+	newClient := domain.HydraClient{ClientID: "new-client"}
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusCreated)
+		json.NewEncoder(w).Encode(newClient)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	created, err := svc.CreateClient(context.Background(), newClient)
+	if err != nil {
+		t.Fatalf("CreateClient failed: %v", err)
+	}
+	if created.ClientID != newClient.ClientID {
+		t.Errorf("expected %s, got %s", newClient.ClientID, created.ClientID)
+	}
+}
+
+func TestHydraAdminService_UpdateClient(t *testing.T) {
+	targetID := "test-client"
+	updatedClient := domain.HydraClient{ClientID: targetID, ClientName: "Updated"}
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPut {
+			t.Errorf("expected PUT, got %s", r.Method)
+		}
+		json.NewEncoder(w).Encode(updatedClient)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	res, err := svc.UpdateClient(context.Background(), targetID, updatedClient)
+	if err != nil {
+		t.Fatalf("UpdateClient failed: %v", err)
+	}
+	if res.ClientName != "Updated" {
+		t.Errorf("expected Updated, got %s", res.ClientName)
+	}
+}
+
+func TestHydraAdminService_DeleteClient(t *testing.T) {
+	targetID := "test-client"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodDelete {
+			t.Errorf("expected DELETE, got %s", r.Method)
+		}
+		w.WriteHeader(http.StatusNoContent)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	err := svc.DeleteClient(context.Background(), targetID)
+	if err != nil {
+		t.Fatalf("DeleteClient failed: %v", err)
+	}
+}
+
+func TestHydraAdminService_ListConsentSessions(t *testing.T) {
+	subject := "user-123"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Query().Get("subject") != subject {
+			t.Errorf("expected subject %s, got %s", subject, r.URL.Query().Get("subject"))
+		}
+		sessions := []domain.HydraConsentSession{{Subject: subject}}
+		json.NewEncoder(w).Encode(sessions)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	res, err := svc.ListConsentSessions(context.Background(), subject, "")
+	if err != nil {
+		t.Fatalf("ListConsentSessions failed: %v", err)
+	}
+	if len(res) != 1 {
+		t.Errorf("expected 1 session, got %d", len(res))
+	}
+}
+
+func TestHydraAdminService_RevokeConsentSessions(t *testing.T) {
+	subject := "user-123"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodDelete {
+			t.Errorf("expected DELETE, got %s", r.Method)
+		}
+		w.WriteHeader(http.StatusNoContent)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	err := svc.RevokeConsentSessions(context.Background(), subject, "client-1")
+	if err != nil {
+		t.Fatalf("RevokeConsentSessions failed: %v", err)
+	}
+}
+
+func TestHydraAdminService_GetConsentRequest(t *testing.T) {
+	challenge := "consent-challenge"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Query().Get("consent_challenge") != challenge {
+			t.Errorf("expected challenge %s, got %s", challenge, r.URL.Query().Get("consent_challenge"))
+		}
+		resp := domain.HydraConsentRequest{Challenge: challenge}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	req, err := svc.GetConsentRequest(context.Background(), challenge)
+	if err != nil {
+		t.Fatalf("GetConsentRequest failed: %v", err)
+	}
+	if req.Challenge != challenge {
+		t.Errorf("expected %s, got %s", challenge, req.Challenge)
+	}
+}
+
+func TestHydraAdminService_RejectConsentRequest(t *testing.T) {
+	challenge := "consent-challenge"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPut {
+			t.Errorf("expected PUT, got %s", r.Method)
+		}
+		resp := struct {
+			RedirectTo string `json:"redirect_to"`
+		}{
+			RedirectTo: "http://redirect",
+		}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	resp, err := svc.RejectConsentRequest(context.Background(), challenge)
+	if err != nil {
+		t.Fatalf("RejectConsentRequest failed: %v", err)
+	}
+	if resp.RedirectTo != "http://redirect" {
+		t.Errorf("expected http://redirect, got %s", resp.RedirectTo)
+	}
+}
+
+func TestHydraAdminService_RejectLoginRequest(t *testing.T) {
+	challenge := "login-challenge"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := struct {
+			RedirectTo string `json:"redirect_to"`
+		}{
+			RedirectTo: "http://redirect",
+		}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	resp, err := svc.RejectLoginRequest(context.Background(), challenge, "error", "desc")
+	if err != nil {
+		t.Fatalf("RejectLoginRequest failed: %v", err)
+	}
+	if resp.RedirectTo != "http://redirect" {
+		t.Errorf("expected http://redirect, got %s", resp.RedirectTo)
+	}
+}
+
+func TestHydraAdminService_GetLoginRequest(t *testing.T) {
+	challenge := "login-challenge"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := domain.HydraLoginRequest{Challenge: challenge}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	req, err := svc.GetLoginRequest(context.Background(), challenge)
+	if err != nil {
+		t.Fatalf("GetLoginRequest failed: %v", err)
+	}
+	if req.Challenge != challenge {
+		t.Errorf("expected %s, got %s", challenge, req.Challenge)
+	}
+}
+
+func TestHydraAdminService_AcceptConsentRequest(t *testing.T) {
+	challenge := "consent-challenge"
+	grantInfo := &domain.HydraConsentRequest{RequestedScope: []string{"openid"}}
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := struct {
+			RedirectTo string `json:"redirect_to"`
+		}{
+			RedirectTo: "http://callback",
+		}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	resp, err := svc.AcceptConsentRequest(context.Background(), challenge, grantInfo, nil)
+	if err != nil {
+		t.Fatalf("AcceptConsentRequest failed: %v", err)
+	}
+	if resp.RedirectTo != "http://callback" {
+		t.Errorf("expected http://callback, got %s", resp.RedirectTo)
+	}
+}
+
+func TestHydraAdminService_AcceptLoginRequest(t *testing.T) {
+	challenge := "login-challenge"
+	subject := "user@example.com"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := struct {
+			RedirectTo string `json:"redirect_to"`
+		}{
+			RedirectTo: "http://callback",
+		}
+		json.NewEncoder(w).Encode(resp)
+	})
+
+	svc := &HydraAdminService{
+		AdminURL:   "http://hydra:4445",
+		HTTPClient: mockHydraClient(handler),
+	}
+
+	resp, err := svc.AcceptLoginRequest(context.Background(), challenge, subject)
+	if err != nil {
+		t.Fatalf("AcceptLoginRequest failed: %v", err)
+	}
+	if resp.RedirectTo != "http://callback" {
+		t.Errorf("expected http://callback, got %s", resp.RedirectTo)
+	}
+}
\ No newline at end of file