diff --git a/app/components/attachment/gallery_item_component.rb b/app/components/attachment/gallery_item_component.rb
index b2f3c5b13..5667074eb 100644
--- a/app/components/attachment/gallery_item_component.rb
+++ b/app/components/attachment/gallery_item_component.rb
@@ -2,11 +2,12 @@
 
 class Attachment::GalleryItemComponent < ApplicationComponent
   include GalleryHelper
-  attr_reader :attachment
+  attr_reader :attachment, :seen_at
 
-  def initialize(attachment:, gallery_demande: false)
+  def initialize(attachment:, gallery_demande: false, seen_at: nil)
     @attachment = attachment
     @gallery_demande = gallery_demande
+    @seen_at = seen_at
   end
 
   def blob
@@ -77,7 +78,7 @@ class Attachment::GalleryItemComponent < ApplicationComponent
   def badge_updated_class
     class_names(
       "fr-badge fr-badge--sm" => true,
-      "fr-badge--new" => updated?
+      "fr-badge--new" => seen_at.present? && updated_at&.>(seen_at)
     )
   end
 end
diff --git a/app/controllers/instructeurs/dossiers_controller.rb b/app/controllers/instructeurs/dossiers_controller.rb
index 575b3d0e4..dec97f6d4 100644
--- a/app/controllers/instructeurs/dossiers_controller.rb
+++ b/app/controllers/instructeurs/dossiers_controller.rb
@@ -386,6 +386,7 @@ module Instructeurs
         .flatten
 
       @gallery_attachments = champs_attachments + commentaires_attachments
+      @pieces_jointes_seen_at = current_instructeur.follows.find_by(dossier: dossier)&.pieces_jointes_seen_at
     end
 
     private
diff --git a/app/views/instructeurs/dossiers/pieces_jointes.html.haml b/app/views/instructeurs/dossiers/pieces_jointes.html.haml
index 222e6e10e..bfc0a0bc0 100644
--- a/app/views/instructeurs/dossiers/pieces_jointes.html.haml
+++ b/app/views/instructeurs/dossiers/pieces_jointes.html.haml
@@ -5,4 +5,4 @@
 .fr-container
   .gallery.gallery-pieces-jointes{ "data-controller": "lightbox" }
     - @gallery_attachments.each do |attachment|
-      = render Attachment::GalleryItemComponent.new(attachment:)
+      = render Attachment::GalleryItemComponent.new(attachment:, seen_at: @pieces_jointes_seen_at)
diff --git a/spec/components/attachment/gallery_item_component_spec.rb b/spec/components/attachment/gallery_item_component_spec.rb
index 3ecb40f29..0f200a76f 100644
--- a/spec/components/attachment/gallery_item_component_spec.rb
+++ b/spec/components/attachment/gallery_item_component_spec.rb
@@ -9,16 +9,23 @@ RSpec.describe Attachment::GalleryItemComponent, type: :component do
   let(:dossier) { create(:dossier, :with_populated_champs, :en_construction, procedure:) }
   let(:filename) { attachment.blob.filename.to_s }
   let(:gallery_demande) { false }
+  let(:seen_at) { nil }
+  let(:now) { Time.zone.parse('01/01/2010') }
 
-  let(:component) { described_class.new(attachment: attachment, gallery_demande:) }
+  let(:component) { described_class.new(attachment: attachment, gallery_demande:, seen_at: seen_at) }
 
   subject { render_inline(component).to_html }
 
+  after { Timecop.return }
+
   context "when attachment is from a piece justificative champ" do
     let(:champ) { dossier.champs.first }
     let(:libelle) { champ.libelle }
     let(:attachment) { champ.piece_justificative_file.attachments.first }
 
+    # Correspond au cas standard où le blob est créé avant le dépôt du dossier
+    before { dossier.touch(:depose_at) }
+
     it "displays libelle, link, tag and renders title" do
       expect(subject).to have_text(libelle)
       expect(subject).not_to have_text('Pièce jointe au message')
@@ -28,9 +35,20 @@ RSpec.describe Attachment::GalleryItemComponent, type: :component do
     end
 
     it "displays when gallery item has been added" do
+      expect(subject).to have_text('Ajoutée le')
+      expect(subject).not_to have_css('.fr-badge--new')
       expect(subject).to have_text(component.helpers.try_format_datetime(attachment.record.created_at, format: :veryshort))
     end
 
+    context "when gallery item has been updated" do
+      # un nouveau blob est créé après modification d'un champ pièce justificative
+      before { attachment.blob.touch(:created_at) }
+
+      it 'displays the right text' do
+        expect(subject).to have_text('Modifiée le')
+      end
+    end
+
     context "when gallery item is in page Demande" do
       let(:gallery_demande) { true }
 
@@ -51,6 +69,30 @@ RSpec.describe Attachment::GalleryItemComponent, type: :component do
         expect(subject).to have_text('Messagerie (usager)')
         expect(component.title).to eq("Pièce jointe au message -- #{filename}")
       end
+
+      context "when instructeur has not seen it yet" do
+        let(:seen_at) { Timecop.freeze(now - 1.day) }
+
+        before do
+          attachment.blob.update(created_at: Timecop.freeze(now))
+        end
+
+        it 'displays datetime in the right style' do
+          expect(subject).to have_css('.fr-badge--new')
+        end
+      end
+
+      context "when instructeur has already seen it" do
+        let!(:seen_at) { Timecop.freeze(now) }
+
+        before do
+          attachment.blob.touch(:created_at)
+        end
+
+        it 'displays datetime in the right style' do
+          expect(subject).not_to have_css('.fr-badge--new')
+        end
+      end
     end
 
     context 'from an instructeur' do