diff --git a/app/models/account_moderation_note.rb b/app/models/account_moderation_note.rb
index ad49b24229..79b8b4d25e 100644
--- a/app/models/account_moderation_note.rb
+++ b/app/models/account_moderation_note.rb
@@ -13,7 +13,7 @@
 #
 
 class AccountModerationNote < ApplicationRecord
-  CONTENT_SIZE_LIMIT = 500
+  CONTENT_SIZE_LIMIT = 2_000
 
   belongs_to :account
   belongs_to :target_account, class_name: 'Account'
diff --git a/app/models/report_note.rb b/app/models/report_note.rb
index b5c40a18b1..7361c97e67 100644
--- a/app/models/report_note.rb
+++ b/app/models/report_note.rb
@@ -13,7 +13,7 @@
 #
 
 class ReportNote < ApplicationRecord
-  CONTENT_SIZE_LIMIT = 500
+  CONTENT_SIZE_LIMIT = 2_000
 
   belongs_to :account
   belongs_to :report, inverse_of: :notes, touch: true
diff --git a/app/views/admin/accounts/show.html.haml b/app/views/admin/accounts/show.html.haml
index 41fcafa29d..bcf7c07314 100644
--- a/app/views/admin/accounts/show.html.haml
+++ b/app/views/admin/accounts/show.html.haml
@@ -62,14 +62,16 @@
   .report-notes
     = render partial: 'admin/report_notes/report_note', collection: @moderation_notes
 
-  = simple_form_for @account_moderation_note, url: admin_account_moderation_notes_path do |f|
-    = f.hidden_field :target_account_id
+  = simple_form_for @account_moderation_note, url: admin_account_moderation_notes_path do |form|
+    = form.hidden_field :target_account_id
+
+    = render 'shared/error_messages', object: @account_moderation_note
 
     .field-group
-      = f.input :content, placeholder: t('admin.reports.notes.placeholder'), rows: 6
+      = form.input :content, input_html: { placeholder: t('admin.reports.notes.placeholder'), maxlength: AccountModerationNote::CONTENT_SIZE_LIMIT, rows: 6, autofocus: @account_moderation_note.errors.any? }
 
     .actions
-      = f.button :button, t('admin.account_moderation_notes.create'), type: :submit
+      = form.button :button, t('admin.account_moderation_notes.create'), type: :submit
 
   %hr.spacer/
 
diff --git a/app/views/admin/reports/show.html.haml b/app/views/admin/reports/show.html.haml
index c880021cff..842aa51597 100644
--- a/app/views/admin/reports/show.html.haml
+++ b/app/views/admin/reports/show.html.haml
@@ -83,15 +83,17 @@
 .report-notes
   = render @report_notes
 
-= simple_form_for @report_note, url: admin_report_notes_path do |f|
-  = f.input :report_id, as: :hidden
+= simple_form_for @report_note, url: admin_report_notes_path do |form|
+  = form.input :report_id, as: :hidden
+
+  = render 'shared/error_messages', object: @report_note
 
   .field-group
-    = f.input :content, placeholder: t('admin.reports.notes.placeholder'), rows: 6
+    = form.input :content, input_html: { placeholder: t('admin.reports.notes.placeholder'), maxlength: ReportNote::CONTENT_SIZE_LIMIT, rows: 6, autofocus: @report_note.errors.any? }
 
   .actions
     - if @report.unresolved?
-      = f.button :button, t('admin.reports.notes.create_and_resolve'), name: :create_and_resolve, type: :submit
+      = form.button :button, t('admin.reports.notes.create_and_resolve'), name: :create_and_resolve, type: :submit
     - else
-      = f.button :button, t('admin.reports.notes.create_and_unresolve'), name: :create_and_unresolve, type: :submit
-    = f.button :button, t('admin.reports.notes.create'), type: :submit
+      = form.button :button, t('admin.reports.notes.create_and_unresolve'), name: :create_and_unresolve, type: :submit
+    = form.button :button, t('admin.reports.notes.create'), type: :submit
diff --git a/config/navigation.rb b/config/navigation.rb
index 791025d526..b6e3f49505 100644
--- a/config/navigation.rb
+++ b/config/navigation.rb
@@ -45,8 +45,8 @@ SimpleNavigation::Configuration.run do |navigation|
     end
 
     n.item :moderation, safe_join([fa_icon('gavel fw'), t('moderation.title')]), nil, if: -> { current_user.can?(:manage_reports, :view_audit_log, :manage_users, :manage_invites, :manage_taxonomies, :manage_federation, :manage_blocks) && !self_destruct } do |s|
-      s.item :reports, safe_join([fa_icon('flag fw'), t('admin.reports.title')]), admin_reports_path, highlights_on: %r{/admin/reports}, if: -> { current_user.can?(:manage_reports) }
-      s.item :accounts, safe_join([fa_icon('users fw'), t('admin.accounts.title')]), admin_accounts_path(origin: 'local'), highlights_on: %r{/admin/accounts|/admin/pending_accounts|/admin/disputes|/admin/users}, if: -> { current_user.can?(:manage_users) }
+      s.item :reports, safe_join([fa_icon('flag fw'), t('admin.reports.title')]), admin_reports_path, highlights_on: %r{/admin/reports|admin/report_notes}, if: -> { current_user.can?(:manage_reports) }
+      s.item :accounts, safe_join([fa_icon('users fw'), t('admin.accounts.title')]), admin_accounts_path(origin: 'local'), highlights_on: %r{/admin/accounts|admin/account_moderation_notes|/admin/pending_accounts|/admin/disputes|/admin/users}, if: -> { current_user.can?(:manage_users) }
       s.item :invites, safe_join([fa_icon('user-plus fw'), t('admin.invites.title')]), admin_invites_path, if: -> { current_user.can?(:manage_invites) }
       s.item :follow_recommendations, safe_join([fa_icon('user-plus fw'), t('admin.follow_recommendations.title')]), admin_follow_recommendations_path, highlights_on: %r{/admin/follow_recommendations}, if: -> { current_user.can?(:manage_taxonomies) }
       s.item :instances, safe_join([fa_icon('cloud fw'), t('admin.instances.title')]), admin_instances_path(limited: limited_federation_mode? ? nil : '1'), highlights_on: %r{/admin/instances|/admin/domain_blocks|/admin/domain_allows}, if: -> { current_user.can?(:manage_federation) }
diff --git a/spec/controllers/admin/account_moderation_notes_controller_spec.rb b/spec/controllers/admin/account_moderation_notes_controller_spec.rb
index 8d24a7af37..5ea546f418 100644
--- a/spec/controllers/admin/account_moderation_notes_controller_spec.rb
+++ b/spec/controllers/admin/account_moderation_notes_controller_spec.rb
@@ -24,10 +24,19 @@ RSpec.describe Admin::AccountModerationNotesController do
       end
     end
 
-    context 'when parameters are invalid' do
+    context 'when the content is too short' do
       let(:params) { { account_moderation_note: { target_account_id: target_account.id, content: '' } } }
 
-      it 'falls to create a note' do
+      it 'fails to create a note' do
+        expect { subject }.to_not change(AccountModerationNote, :count)
+        expect(response).to render_template 'admin/accounts/show'
+      end
+    end
+
+    context 'when the content is too long' do
+      let(:params) { { account_moderation_note: { target_account_id: target_account.id, content: 'test' * AccountModerationNote::CONTENT_SIZE_LIMIT } } }
+
+      it 'fails to create a note' do
         expect { subject }.to_not change(AccountModerationNote, :count)
         expect(response).to render_template 'admin/accounts/show'
       end
diff --git a/spec/controllers/admin/report_notes_controller_spec.rb b/spec/controllers/admin/report_notes_controller_spec.rb
index 4ddf4a4e24..8d5b5c7aec 100644
--- a/spec/controllers/admin/report_notes_controller_spec.rb
+++ b/spec/controllers/admin/report_notes_controller_spec.rb
@@ -22,7 +22,7 @@ describe Admin::ReportNotesController do
         let(:account_id) { nil }
 
         context 'when create_and_resolve flag is on' do
-          let(:params) { { report_note: { content: 'test content', report_id: report.id }, create_and_resolve: nil } }
+          let(:params) { { report_note: { report_id: report.id, content: 'test content' }, create_and_resolve: nil } }
 
           it 'creates a report note and resolves report' do
             expect { subject }.to change(ReportNote, :count).by(1)
@@ -32,7 +32,7 @@ describe Admin::ReportNotesController do
         end
 
         context 'when create_and_resolve flag is false' do
-          let(:params) { { report_note: { content: 'test content', report_id: report.id } } }
+          let(:params) { { report_note: { report_id: report.id, content: 'test content' } } }
 
           it 'creates a report note and does not resolve report' do
             expect { subject }.to change(ReportNote, :count).by(1)
@@ -47,7 +47,7 @@ describe Admin::ReportNotesController do
         let(:account_id) { user.account.id }
 
         context 'when create_and_unresolve flag is on' do
-          let(:params) { { report_note: { content: 'test content', report_id: report.id }, create_and_unresolve: nil } }
+          let(:params) { { report_note: { report_id: report.id, content: 'test content' }, create_and_unresolve: nil } }
 
           it 'creates a report note and unresolves report' do
             expect { subject }.to change(ReportNote, :count).by(1)
@@ -57,7 +57,7 @@ describe Admin::ReportNotesController do
         end
 
         context 'when create_and_unresolve flag is false' do
-          let(:params) { { report_note: { content: 'test content', report_id: report.id } } }
+          let(:params) { { report_note: { report_id: report.id, content: 'test content' } } }
 
           it 'creates a report note and does not unresolve report' do
             expect { subject }.to change(ReportNote, :count).by(1)
@@ -68,12 +68,24 @@ describe Admin::ReportNotesController do
       end
     end
 
-    context 'when parameter is invalid' do
-      let(:params) { { report_note: { content: '', report_id: report.id } } }
+    context 'when content is too short' do
+      let(:params) { { report_note: { report_id: report.id, content: '' } } }
       let(:action_taken) { nil }
       let(:account_id) { nil }
 
       it 'renders admin/reports/show' do
+        expect { subject }.to_not change(ReportNote, :count)
+        expect(subject).to render_template 'admin/reports/show'
+      end
+    end
+
+    context 'when content is too long' do
+      let(:params) { { report_note: { report_id: report.id, content: 'test' * ReportNote::CONTENT_SIZE_LIMIT } } }
+      let(:action_taken) { nil }
+      let(:account_id) { nil }
+
+      it 'renders admin/reports/show' do
+        expect { subject }.to_not change(ReportNote, :count)
         expect(subject).to render_template 'admin/reports/show'
       end
     end