diff --git a/release-notes/CREDITS b/release-notes/CREDITS
index a898cf21..f6481e84 100644
--- a/release-notes/CREDITS
+++ b/release-notes/CREDITS
@@ -168,3 +168,5 @@ Christian Beikov (@beikov)
   (3.3.0)
  * Fixed #883: Translate `XMLStreamReader` creation errors to `StreamReadException`
   (3.3.0)
+ * Fixed #886: Escape names already starting with prefix in `Base64NameProcessor`
+  (3.3.0)
diff --git a/release-notes/VERSION b/release-notes/VERSION
index 082c59c2..1f878a56 100644
--- a/release-notes/VERSION
+++ b/release-notes/VERSION
@@ -18,6 +18,8 @@ Version: 3.x (for earlier see VERSION-2.x)
 #883: Translate `XMLStreamReader` creation errors to `StreamReadException`
   (restores guard lost in 3.x port; see 2.x `_createParser(byte[])` for #618)
  (fix by @Sahana2524)
+#886: Escape names already starting with prefix in `Base64NameProcessor`
+ (fix by @Sahana2524)
 
 3.2.2 (not yet released)
 
diff --git a/src/main/java/tools/jackson/dataformat/xml/XmlNameProcessors.java b/src/main/java/tools/jackson/dataformat/xml/XmlNameProcessors.java
index e13a2b41..1abef18e 100644
--- a/src/main/java/tools/jackson/dataformat/xml/XmlNameProcessors.java
+++ b/src/main/java/tools/jackson/dataformat/xml/XmlNameProcessors.java
@@ -118,8 +118,9 @@ public static XmlNameProcessor newReplacementProcessor() {
      * </DTO>
      * }</pre>
      *<p>
-     * NOTE: you must ensure that no incoming element or attribute name starts
-     * with {@code prefix}, otherwise decoding will not work.
+     * NOTE: names that already start with {@code prefix} are escaped as well, even
+     * though they are otherwise valid, so that decoding cannot confuse them with
+     * names this processor encoded.
      *
      * @param prefix The prefix to use for name that are escaped
      */
@@ -197,7 +198,12 @@ public Base64NameProcessor(String prefix) {
 
         @Override
         public void encodeName(XmlName name) {
-            if (!VALID_XML_NAME.matcher(name.localPart).matches()) {
+            // Names already starting with the prefix have to be escaped as well, even
+            // when otherwise valid: decodeName() base64-decodes anything carrying the
+            // prefix, so passing such a name through as-is would decode it into a
+            // different name than was written.
+            if (!VALID_XML_NAME.matcher(name.localPart).matches()
+                    || name.localPart.startsWith(_prefix)) {
                 name.localPart = _prefix + new String(BASE64_ENCODER.encode(name.localPart.getBytes(UTF_8)), UTF_8);
             }
         }
diff --git a/src/test/java/tools/jackson/dataformat/xml/misc/XmlNameEscapeTest.java b/src/test/java/tools/jackson/dataformat/xml/misc/XmlNameEscapeTest.java
index e47f313d..cd442a44 100644
--- a/src/test/java/tools/jackson/dataformat/xml/misc/XmlNameEscapeTest.java
+++ b/src/test/java/tools/jackson/dataformat/xml/misc/XmlNameEscapeTest.java
@@ -154,6 +154,42 @@ public void testAlwaysOnBase64UndecodableNameFailsAsReadException() throws Excep
         assertNotEquals(TokenStreamLocation.NA, e.getLocation());
     }
 
+    // A name that is a valid XML name but already starts with the magic prefix has
+    // to be escaped too: decoding keys off that prefix, so writing such a name
+    // through as-is makes it read back as a different name than was written.
+    @Test
+    public void testBase64PrefixedNamesRoundTrip() throws Exception {
+        DTO dto = new DTO();
+
+        // would otherwise read back as "admin"
+        dto.badMap.put("base64_tag_YWRtaW4", "xyz");
+        // valid XML name, but not valid base64 past the prefix
+        dto.badMap.put("base64_tag_hello", "bar");
+        dto.badMap.put("plain", "abc");
+
+        XmlMapper mapper = XmlMapper.builder(
+                xmlFactory(XmlNameProcessors.newBase64Processor())
+        ).build();
+
+        final String res = mapper.writeValueAsString(dto);
+        DTO reversed = mapper.readValue(res, DTO.class);
+        assertEquals(dto, reversed);
+    }
+
+    @Test
+    public void testBase64CustomPrefixedNameRoundTrips() throws Exception {
+        DTO dto = new DTO();
+        dto.badMap.put("esc_YWRtaW4", "xyz");
+
+        XmlMapper mapper = XmlMapper.builder(
+                xmlFactory(XmlNameProcessors.newBase64Processor("esc_"))
+        ).build();
+
+        final String res = mapper.writeValueAsString(dto);
+        DTO reversed = mapper.readValue(res, DTO.class);
+        assertEquals(dto, reversed);
+    }
+
     protected XmlFactory xmlFactory(XmlNameProcessor proc) {
         return XmlFactory.builder().xmlNameProcessor(proc).build();
     }