diff --git a/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtil.java b/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtil.java
index e022c8696..0fd98e91a 100644
--- a/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtil.java
+++ b/opc-ua-stack/stack-core/src/main/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtil.java
@@ -496,6 +496,17 @@ public static void checkValidity(X509Certificate certificate, boolean endEntity)
         }
     }
 
+    /**
+     * Creates a predicate to compare a hostname against a SubjectAltName DNSName entry in a
+     * certificate. The comparison is case-insensitive, following RFC 3986.
+     *
+     * @param hostname the hostname to compare against.
+     * @return a predicate that returns {@code true} if the hostname matches the DNSName entry.
+     */
+    private static Predicate<Object> hostnameValidationPredicate(String hostname) {
+        return input -> input instanceof String && hostname.equalsIgnoreCase((String) input);
+    }
+
     /**
      * Validate that one of {@code hostNames} matches a SubjectAltName DNSName or IPAddress entry in the certificate.
      *
@@ -513,7 +524,7 @@ public static void checkHostnameOrIpAddress(
                 return checkSubjectAltNameField(
                     certificate,
                     SUBJECT_ALT_NAME_DNS_NAME,
-                    n::equals
+                    hostnameValidationPredicate(n)
                 );
             } catch (Throwable t) {
                 return false;
diff --git a/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtilTest.java b/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtilTest.java
index c14573793..2bacb4d71 100644
--- a/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtilTest.java
+++ b/opc-ua-stack/stack-core/src/test/java/org/eclipse/milo/opcua/stack/core/util/validation/CertificateValidationUtilTest.java
@@ -43,6 +43,7 @@
 import static com.google.common.collect.Sets.newHashSet;
 import static java.util.Collections.emptySet;
 import static org.eclipse.milo.opcua.stack.core.util.validation.CertificateValidationUtil.buildTrustedCertPath;
+import static org.eclipse.milo.opcua.stack.core.util.validation.CertificateValidationUtil.checkHostnameOrIpAddress;
 import static org.eclipse.milo.opcua.stack.core.util.validation.CertificateValidationUtil.validateTrustedCertPath;
 import static org.testng.Assert.assertEquals;
 import static org.testng.Assert.assertFalse;
@@ -451,6 +452,15 @@ public void testUriWithSpaces() throws Exception {
         );
     }
 
+    @Test
+    public void testHostnameWithCaseInsensitive() throws Exception {
+        String hostname = "digitalpetri.com";
+        checkHostnameOrIpAddress(createSelfSignedCertificate("digitalpetri.com"), hostname);
+        checkHostnameOrIpAddress(createSelfSignedCertificate("DIGITALPETRI.COM"), hostname);
+        checkHostnameOrIpAddress(createSelfSignedCertificate("DIGITALPETRI.com"), hostname);
+        checkHostnameOrIpAddress(createSelfSignedCertificate("DigitalPetri.com"), hostname);
+    }
+
     private X509CRL generateCrl(X509Certificate ca, PrivateKey caPrivateKey, X509Certificate... revoked) throws Exception {
         X509v2CRLBuilder builder = new X509v2CRLBuilder(
             new X500Name(ca.getSubjectDN().getName()),
@@ -487,4 +497,14 @@ private X509Certificate getCertificate(String alias) throws KeyStoreException {
         return certificate;
     }
 
+    private static X509Certificate createSelfSignedCertificate(String dnsName) throws Exception {
+        KeyPair keyPair = SelfSignedCertificateGenerator.generateRsaKeyPair(2048);
+
+        SelfSignedCertificateBuilder builder = new SelfSignedCertificateBuilder(keyPair)
+            .setApplicationUri("urn:eclipse:milo:test")
+            .addDnsName(dnsName);
+
+        return builder.build();
+    }
+
 }