diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7fe268d1..73ee297a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,11 +4,17 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Changed
+
 - Reduce CRD size from `637KB` to `105KB` by accepting arbitrary YAML input instead of the underlying schema for the following fields ([#664]):
   - `podOverrides`
   - `affinity`
   - `extraVolumes`
 
+### Removed
+
+- Removed support for NiFi versions 1.21.0 and 1.25.0 ([#XXX]).
+
 [#664]: https://github.com/stackabletech/nifi-operator/pull/664
 
 ## [24.7.0] - 2024-07-24
diff --git a/docs/modules/nifi/pages/usage_guide/updating.adoc b/docs/modules/nifi/pages/usage_guide/updating.adoc
index 333e660d..47633308 100644
--- a/docs/modules/nifi/pages/usage_guide/updating.adoc
+++ b/docs/modules/nifi/pages/usage_guide/updating.adoc
@@ -1,7 +1,7 @@
 = Updating NiFi
 
 Updating (or downgrading for that matter) the deployed version of NiFi is as simple as changing the version stated in the CRD.
-Continuing the example above, to change the deployed version from `1.27.0` to `1.25.0` you'd simply deploy the following CRD.
+Continuing the example above, to change the deployed version from `1.25.0` to `1.27.0` you'd simply deploy the following CRD.
 
 [source,yaml]
 ----
@@ -11,18 +11,7 @@ metadata:
   name: simple-nifi
 spec:
   image:
-    productVersion: 1.25.0 # <1>
-  clusterConfig:
-    authentication:
-      - authenticationClass: simple-nifi-admin-user
-    listenerClass: external-unstable
-    sensitiveProperties:
-      keySecret: nifi-sensitive-property-key
-    zookeeperConfigMapName: simple-nifi-znode
-  nodes:
-    roleGroups:
-      default:
-        replicas: 3
+    productVersion: 1.27.0 # <1>
 ----
 
 <1> Change the NiFi version here
diff --git a/docs/modules/nifi/partials/supported-versions.adoc b/docs/modules/nifi/partials/supported-versions.adoc
index c3f0b6eb..efad3d9e 100644
--- a/docs/modules/nifi/partials/supported-versions.adoc
+++ b/docs/modules/nifi/partials/supported-versions.adoc
@@ -2,7 +2,5 @@
 // This is a separate file, since it is used by both the direct NiFi-Operator documentation, and the overarching
 // Stackable Platform documentation.
 
-- 2.0.0-M4 (experimental)
+- 2.0.0-M4 (experimental) - Please note that you need to upgrade to at least 1.27.x before upgrading to 2.x.x!
 - 1.27.0 (LTS)
-- 1.25.0
-- 1.21.0 (deprecated)
diff --git a/tests/test-definition.yaml b/tests/test-definition.yaml
index 83c0d4a2..005b19ca 100644
--- a/tests/test-definition.yaml
+++ b/tests/test-definition.yaml
@@ -12,8 +12,6 @@ dimensions:
       - 3.9.2
   - name: nifi
     values:
-      - 1.21.0
-      - 1.25.0
       - 1.27.0
       - 2.0.0-M4
       # Alternatively, if you want to use a custom image, append a comma and the full image name to the product version