diff --git a/src/lib/kyc-status-log.ts b/src/lib/kyc-status-log.ts
index 475e176..2952443 100644
--- a/src/lib/kyc-status-log.ts
+++ b/src/lib/kyc-status-log.ts
@@ -5,6 +5,9 @@ import { truncateWalletAddress } from "./kyc";
 /** The administrative action that produced a KYC status change. */
 export type KYCStatusChangeAction = "approve" | "reject" | "revoke";
 
+/** The stable category of a KYC review failure. */
+export type KYCReviewFailureCategory = "unauthorized" | "user_not_found" | "invalid_state" | "database_error";
+
 export interface KYCStatusChangeInput {
   /** Wallet address of the user whose KYC status changed. */
   wallet: string;
@@ -51,3 +54,32 @@ export function logKYCStatusChange(logger: AppLogger, input: KYCStatusChangeInpu
     ...(input.reason ? { reason: input.reason } : {}),
   });
 }
+
+export interface KYCReviewFailureInput {
+  /** Internal id of the user being reviewed, if known. */
+  userId?: string;
+  /** Internal id of the reviewing admin, if known. */
+  reviewerId?: string;
+  /** Which admin action failed. */
+  action: KYCStatusChangeAction;
+  /** The stable category of the failure. */
+  failureCategory: KYCReviewFailureCategory;
+  /** A correlation identifier for the request, if available. */
+  correlationId?: string;
+  /** Any error message or code. */
+  errorDetails?: string;
+}
+
+/**
+ * Audit log for failed KYC review decisions.
+ */
+export function logKYCReviewFailure(logger: AppLogger, input: KYCReviewFailureInput): void {
+  logger.error("KYC review failed", {
+    ...(input.userId ? { user_id: input.userId } : {}),
+    ...(input.reviewerId ? { reviewer_id: input.reviewerId } : {}),
+    action: input.action,
+    failure_category: input.failureCategory,
+    ...(input.correlationId ? { correlation_id: input.correlationId } : {}),
+    ...(input.errorDetails ? { error_details: input.errorDetails } : {}),
+  });
+}
diff --git a/src/routes/admin/approve-kyc.ts b/src/routes/admin/approve-kyc.ts
index 2b9f3af..543dc90 100644
--- a/src/routes/admin/approve-kyc.ts
+++ b/src/routes/admin/approve-kyc.ts
@@ -2,7 +2,7 @@ import { Request, Response } from "express";
 import { DataSource } from "typeorm";
 import { User } from "@/models/User.model";
 import { KYCStatus } from "@/types/enums";
-import { logKYCStatusChange } from "@/lib/kyc-status-log";
+import { logKYCStatusChange, logKYCReviewFailure } from "@/lib/kyc-status-log";
 import { logger } from "@/observability/logger";
 
 interface ApproveKYCBody {
@@ -13,7 +13,16 @@ interface ApproveKYCBody {
 export async function approveKYC(req: Request<unknown, unknown, ApproveKYCBody>, res: Response, dataSource: DataSource) {
   try {
     const adminKey = req.headers["x-admin-key"];
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+
     if (adminKey !== process.env.ADMIN_API_KEY) {
+      logKYCReviewFailure(logger, {
+        userId: req.body?.userId,
+        reviewerId: req.body?.reviewerId,
+        action: "approve",
+        failureCategory: "unauthorized",
+        correlationId,
+      });
       return res.status(401).json({ error: "Unauthorized" });
     }
 
@@ -22,6 +31,13 @@ export async function approveKYC(req: Request<unknown, unknown, ApproveKYCBody>,
     const userRepo = dataSource.getRepository(User);
     const user = await userRepo.findOneBy({ id: userId });
     if (!user) {
+      logKYCReviewFailure(logger, {
+        userId,
+        reviewerId,
+        action: "approve",
+        failureCategory: "user_not_found",
+        correlationId,
+      });
       return res.status(404).json({ error: "User not found" });
     }
 
@@ -45,6 +61,16 @@ export async function approveKYC(req: Request<unknown, unknown, ApproveKYCBody>,
 
     return res.json({ success: true });
   } catch (err: unknown) {
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+    logKYCReviewFailure(logger, {
+      userId: req.body?.userId,
+      reviewerId: req.body?.reviewerId,
+      action: "approve",
+      failureCategory: "database_error",
+      correlationId,
+      errorDetails: err instanceof Error ? err.message : String(err),
+    });
+
     const appErr = err as { status?: number; code?: string; message?: string };
     return res.status(appErr.status ?? 500).json({
       error: {
diff --git a/src/routes/admin/reject-kyc.ts b/src/routes/admin/reject-kyc.ts
index 75ac4a1..5abe1af 100644
--- a/src/routes/admin/reject-kyc.ts
+++ b/src/routes/admin/reject-kyc.ts
@@ -2,7 +2,7 @@ import { Request, Response } from "express";
 import { DataSource } from "typeorm";
 import { User } from "@/models/User.model";
 import { KYCStatus } from "@/types/enums";
-import { logKYCStatusChange } from "@/lib/kyc-status-log";
+import { logKYCStatusChange, logKYCReviewFailure } from "@/lib/kyc-status-log";
 import { logger } from "@/observability/logger";
 
 interface RejectKYCBody {
@@ -14,7 +14,16 @@ interface RejectKYCBody {
 export async function rejectKYC(req: Request<unknown, unknown, RejectKYCBody>, res: Response, dataSource: DataSource) {
   try {
     const adminKey = req.headers["x-admin-key"];
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+
     if (adminKey !== process.env.ADMIN_API_KEY) {
+      logKYCReviewFailure(logger, {
+        userId: req.body?.userId,
+        reviewerId: req.body?.reviewerId,
+        action: "reject",
+        failureCategory: "unauthorized",
+        correlationId,
+      });
       return res.status(401).json({ error: "Unauthorized" });
     }
 
@@ -23,6 +32,13 @@ export async function rejectKYC(req: Request<unknown, unknown, RejectKYCBody>, r
     const userRepo = dataSource.getRepository(User);
     const user = await userRepo.findOneBy({ id: userId });
     if (!user) {
+      logKYCReviewFailure(logger, {
+        userId,
+        reviewerId,
+        action: "reject",
+        failureCategory: "user_not_found",
+        correlationId,
+      });
       return res.status(404).json({ error: "User not found" });
     }
 
@@ -47,6 +63,16 @@ export async function rejectKYC(req: Request<unknown, unknown, RejectKYCBody>, r
 
     return res.json({ success: true });
   } catch (err: unknown) {
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+    logKYCReviewFailure(logger, {
+      userId: req.body?.userId,
+      reviewerId: req.body?.reviewerId,
+      action: "reject",
+      failureCategory: "database_error",
+      correlationId,
+      errorDetails: err instanceof Error ? err.message : String(err),
+    });
+
     const appErr = err as { status?: number; code?: string; message?: string };
     return res.status(appErr.status ?? 500).json({
       error: {
diff --git a/src/routes/admin/revoke-kyc.ts b/src/routes/admin/revoke-kyc.ts
index 84716ad..17ecfff 100644
--- a/src/routes/admin/revoke-kyc.ts
+++ b/src/routes/admin/revoke-kyc.ts
@@ -2,7 +2,7 @@ import { Request, Response } from "express";
 import { DataSource } from "typeorm";
 import { User } from "@/models/User.model";
 import { KYCStatus } from "@/types/enums";
-import { logKYCStatusChange } from "@/lib/kyc-status-log";
+import { logKYCStatusChange, logKYCReviewFailure } from "@/lib/kyc-status-log";
 import { logger } from "@/observability/logger";
 
 interface RevokeKYCBody {
@@ -23,7 +23,16 @@ interface RevokeKYCBody {
 export async function revokeKYC(req: Request<unknown, unknown, RevokeKYCBody>, res: Response, dataSource: DataSource) {
   try {
     const adminKey = req.headers["x-admin-key"];
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+
     if (adminKey !== process.env.ADMIN_API_KEY) {
+      logKYCReviewFailure(logger, {
+        userId: req.body?.userId,
+        reviewerId: req.body?.reviewerId,
+        action: "revoke",
+        failureCategory: "unauthorized",
+        correlationId,
+      });
       return res.status(401).json({ error: "Unauthorized" });
     }
 
@@ -32,11 +41,26 @@ export async function revokeKYC(req: Request<unknown, unknown, RevokeKYCBody>, r
     const userRepo = dataSource.getRepository(User);
     const user = await userRepo.findOneBy({ id: userId });
     if (!user) {
+      logKYCReviewFailure(logger, {
+        userId,
+        reviewerId,
+        action: "revoke",
+        failureCategory: "user_not_found",
+        correlationId,
+      });
       return res.status(404).json({ error: "User not found" });
     }
 
     const previousStatus = user.kycStatus;
     if (previousStatus !== KYCStatus.APPROVED) {
+      logKYCReviewFailure(logger, {
+        userId,
+        reviewerId,
+        action: "revoke",
+        failureCategory: "invalid_state",
+        correlationId,
+        errorDetails: `Cannot revoke KYC for a user whose status is ${previousStatus}.`,
+      });
       return res.status(409).json({
         error: {
           code: "KYC_NOT_APPROVED",
@@ -63,6 +87,16 @@ export async function revokeKYC(req: Request<unknown, unknown, RevokeKYCBody>, r
 
     return res.json({ success: true });
   } catch (err: unknown) {
+    const correlationId = req.headers["x-request-id"] as string | undefined;
+    logKYCReviewFailure(logger, {
+      userId: req.body?.userId,
+      reviewerId: req.body?.reviewerId,
+      action: "revoke",
+      failureCategory: "database_error",
+      correlationId,
+      errorDetails: err instanceof Error ? err.message : String(err),
+    });
+
     const appErr = err as { status?: number; code?: string; message?: string };
     return res.status(appErr.status ?? 500).json({
       error: {