diff --git a/packages/safe-chain/src/registryProxy/certBundle.js b/packages/safe-chain/src/registryProxy/certBundle.js
index 956279d..9b0c7bf 100644
--- a/packages/safe-chain/src/registryProxy/certBundle.js
+++ b/packages/safe-chain/src/registryProxy/certBundle.js
@@ -6,6 +6,7 @@ import certifi from "certifi";
 import tls from "node:tls";
 import { X509Certificate } from "node:crypto";
 import { getCaCertPath } from "./certUtils.js";
+import { ui } from "../environment/userInteraction.js";
 
 /**
  * Check if a PEM string contains only parsable cert blocks.
@@ -93,3 +94,68 @@ export function getCombinedCaBundlePath() {
   cachedPath = target;
   return cachedPath;
 }
+
+/**
+ * Read user certificate file.
+ * @param {string} certPath - Path to certificate file
+ * @returns {string | null} Certificate PEM content or null if invalid/unreadable
+ */
+function readUserCertificateFile(certPath) {
+  try {
+    // Validate path is a string and not attempting path traversal
+    if (typeof certPath !== "string" || certPath.includes("..") || certPath.startsWith("/")) {
+      return null;
+    }
+
+    if (!fs.existsSync(certPath)) {
+      return null;
+    }
+
+    const certPathAbsolute = path.resolve(certPath);
+    // Verify it's an absolute path (cross-platform)
+    if (!path.isAbsolute(certPathAbsolute)) {
+      return null;
+    }
+
+    const content = fs.readFileSync(certPathAbsolute, "utf8");
+    return content && isParsable(content) ? content : null;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Combine user's existing NODE_EXTRA_CA_CERTS with Safe Chain's CA certificate.
+ * If user has NODE_EXTRA_CA_CERTS set, it's merged with Safe Chain CA.
+ * 
+ * @param {string | undefined} userCertPath - User's existing NODE_EXTRA_CA_CERTS path (if any)
+ * @returns {string} Path to the final CA bundle
+ */
+export function getCombinedCaBundlePathWithUserCerts(userCertPath) {
+  const parts = [];
+
+  // 1) Add Safe Chain CA (for MITM'd registries)
+  const safeChainPath = getCaCertPath();
+  try {
+    const safeChainPem = fs.readFileSync(safeChainPath, "utf8");
+    if (isParsable(safeChainPem)) parts.push(safeChainPem.trim());
+  } catch {
+    // Ignore if Safe Chain CA is not available
+  }
+
+  // 2) Add user's certificates if provided
+  if (userCertPath) {
+    const userPem = readUserCertificateFile(userCertPath);
+    if (userPem) {
+      parts.push(userPem.trim());
+      ui.writeWarning(`Safe-chain: Merging user's NODE_EXTRA_CA_CERTS from ${userCertPath}`);
+    } else {
+      ui.writeWarning(`Safe-chain: Could not read or parse user's NODE_EXTRA_CA_CERTS from ${userCertPath}`);
+    }
+  }
+
+  const finalCombined = parts.filter(Boolean).join("\n");
+  const target = path.join(os.tmpdir(), `safe-chain-ca-bundle-${Date.now()}.pem`);
+  fs.writeFileSync(target, finalCombined, { encoding: "utf8" });
+  return target;
+}
diff --git a/packages/safe-chain/src/registryProxy/registryProxy.js b/packages/safe-chain/src/registryProxy/registryProxy.js
index 6f11207..ae7a47e 100644
--- a/packages/safe-chain/src/registryProxy/registryProxy.js
+++ b/packages/safe-chain/src/registryProxy/registryProxy.js
@@ -2,7 +2,7 @@ import * as http from "http";
 import { tunnelRequest } from "./tunnelRequestHandler.js";
 import { mitmConnect } from "./mitmRequestHandler.js";
 import { handleHttpProxyRequest } from "./plainHttpProxy.js";
-import { getCaCertPath } from "./certUtils.js";
+import { getCombinedCaBundlePathWithUserCerts } from "./certBundle.js";
 import { ui } from "../environment/userInteraction.js";
 import chalk from "chalk";
 import { createInterceptorForUrl } from "./interceptors/createInterceptorForEcoSystem.js";
@@ -37,10 +37,13 @@ function getSafeChainProxyEnvironmentVariables() {
   }
 
   const proxyUrl = `http://localhost:${state.port}`;
+  const userNodeExtraCaCerts = process.env.NODE_EXTRA_CA_CERTS;
+  const caCertPath = getCombinedCaBundlePathWithUserCerts(userNodeExtraCaCerts);
+
   return {
     HTTPS_PROXY: proxyUrl,
     GLOBAL_AGENT_HTTP_PROXY: proxyUrl,
-    NODE_EXTRA_CA_CERTS: getCaCertPath(),
+    NODE_EXTRA_CA_CERTS: caCertPath,
   };
 }