diff --git a/app/assets/stylesheets/new_design/dossier_show.scss b/app/assets/stylesheets/new_design/dossier_show.scss
index def3e15d3..be12db19e 100644
--- a/app/assets/stylesheets/new_design/dossier_show.scss
+++ b/app/assets/stylesheets/new_design/dossier_show.scss
@@ -38,4 +38,15 @@
   .messagerie-explanation {
     margin-bottom: $default-padding * 2;
   }
+
+  .latest-message-section {
+    display: flex;
+    flex-direction: column;
+    max-width: 700px;
+    margin-bottom: $default-padding * 2;
+
+    .button.send {
+      align-self: flex-end;
+    }
+  }
 }
diff --git a/app/assets/stylesheets/new_design/message.scss b/app/assets/stylesheets/new_design/message.scss
index 025a7783e..7c87e763e 100644
--- a/app/assets/stylesheets/new_design/message.scss
+++ b/app/assets/stylesheets/new_design/message.scss
@@ -9,6 +9,10 @@
   background: #FFFFFF;
   border-radius: 3px;
 
+  &.inverted-background {
+    background: $light-grey;
+  }
+
   .person-icon {
     margin-right: $default-spacer;
   }
diff --git a/app/assets/stylesheets/new_design/status_overview.scss b/app/assets/stylesheets/new_design/status_overview.scss
index 49ad8a55b..55643b1d3 100644
--- a/app/assets/stylesheets/new_design/status_overview.scss
+++ b/app/assets/stylesheets/new_design/status_overview.scss
@@ -3,6 +3,7 @@
 
 .status-overview {
   text-align: center;
+  margin-bottom: $default-padding * 2;
 }
 
 .status-timeline {
diff --git a/app/helpers/commentaire_helper.rb b/app/helpers/commentaire_helper.rb
index 7702e85c6..f42450024 100644
--- a/app/helpers/commentaire_helper.rb
+++ b/app/helpers/commentaire_helper.rb
@@ -5,6 +5,14 @@ module CommentaireHelper
     end
   end
 
+  def commentaire_answer_action(commentaire, connected_user)
+    if commentaire_is_from_me(commentaire, connected_user)
+      "Envoyer un message à l’instructeur"
+    else
+      "Répondre dans la messagerie"
+    end
+  end
+
   def commentaire_is_from_guest(commentaire)
     commentaire.dossier.invites.map(&:email).include?(commentaire.email)
   end
diff --git a/app/views/new_user/dossiers/show.html.haml b/app/views/new_user/dossiers/show.html.haml
index e6e17707c..b94a0686f 100644
--- a/app/views/new_user/dossiers/show.html.haml
+++ b/app/views/new_user/dossiers/show.html.haml
@@ -5,3 +5,13 @@
 
   .container
     = render partial: 'new_user/dossiers/show/status_overview', locals: { dossier: @dossier }
+
+    - latest_message = @dossier.commentaires.last
+    - if latest_message.present?
+      .latest-message-section
+        %h3.tab-title Dernier message
+
+        .message.inverted-background
+          = render partial: "shared/dossiers/messages/message", locals: { commentaire: latest_message, connected_user: current_user, messagerie_seen_at: nil }
+
+        = link_to commentaire_answer_action(latest_message, current_user), messagerie_dossier_url(@dossier, anchor: 'new_commentaire'), class: 'button send'
diff --git a/spec/features/new_user/dossier_details_spec.rb b/spec/features/new_user/dossier_details_spec.rb
index d6644e634..41575988b 100644
--- a/spec/features/new_user/dossier_details_spec.rb
+++ b/spec/features/new_user/dossier_details_spec.rb
@@ -4,7 +4,7 @@ describe 'Dossier details:' do
     tdcs = [create(:type_de_champ, libelle: 'texte obligatoire')]
     create(:procedure, :published, :for_individual, types_de_champ: tdcs)
   end
-  let(:dossier) { create(:dossier, :en_construction, :for_individual, user: user, procedure: simple_procedure) }
+  let(:dossier) { create(:dossier, :en_construction, :for_individual, :with_commentaires, user: user, procedure: simple_procedure) }
 
   before do
     Flipflop::FeatureSet.current.test!.switch!(:new_dossier_details, true)
@@ -16,6 +16,7 @@ describe 'Dossier details:' do
     expect(page).to have_current_path(dossier_path(dossier))
     expect(page).to have_content(dossier.id)
     expect(page).to have_selector('.status-explanation')
+    expect(page).to have_text(dossier.commentaires.last.body)
   end
 
   scenario 'the user can see and edit dossier before instruction' do
diff --git a/spec/helpers/commentaire_helper_spec.rb b/spec/helpers/commentaire_helper_spec.rb
index ec1430f22..36d235f42 100644
--- a/spec/helpers/commentaire_helper_spec.rb
+++ b/spec/helpers/commentaire_helper_spec.rb
@@ -7,16 +7,30 @@ RSpec.describe CommentaireHelper, type: :helper do
     subject { commentaire_is_from_me_class(commentaire, me) }
 
     context "when commentaire is from me" do
-      let(:me) { "michel@pref.fr" }
+      let(:me) { User.new(email: "michel@pref.fr") }
       it { is_expected.to eq("from-me") }
     end
 
     context "when commentaire is not from me" do
-      let(:me) { "roger@usager.fr" }
+      let(:me) { User.new(email: "roger@usager.fr") }
       it { is_expected.to eq nil }
     end
   end
 
+  describe '.commentaire_answer_action' do
+    subject { commentaire_answer_action(commentaire, me) }
+
+    context "when commentaire is from me" do
+      let(:me) { User.new(email: "michel@pref.fr") }
+      it { is_expected.to include('Envoyer') }
+    end
+
+    context "when commentaire is not from me" do
+      let(:me) { User.new(email: "roger@usager.fr") }
+      it { is_expected.to include('Répondre') }
+    end
+  end
+
   describe '.commentaire_is_from_guest' do
     let(:dossier) { create(:dossier) }
     let!(:guest) { create(:invite_user, dossier: dossier) }
diff --git a/spec/views/new_user/dossiers/show.html.haml_spec.rb b/spec/views/new_user/dossiers/show.html.haml_spec.rb
index 303f1f244..977b5677b 100644
--- a/spec/views/new_user/dossiers/show.html.haml_spec.rb
+++ b/spec/views/new_user/dossiers/show.html.haml_spec.rb
@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe 'new_user/dossiers/show.html.haml', type: :view do
-  let(:dossier) { create(:dossier, :en_construction, procedure: create(:procedure)) }
+  let(:dossier) { create(:dossier, :en_construction) }
 
   before do
     sign_in dossier.user
@@ -14,4 +14,15 @@ describe 'new_user/dossiers/show.html.haml', type: :view do
     expect(rendered).to have_text("Dossier nº #{dossier.id}")
     expect(rendered).to have_selector('.status-overview')
   end
+
+  context 'with messages' do
+    let(:first_message) { create(:commentaire, body: 'Premier message') }
+    let(:last_message)  { create(:commentaire, body: 'Second message') }
+    let(:dossier) { create(:dossier, :en_construction, commentaires: [first_message, last_message]) }
+
+    it 'displays the last message' do
+      expect(rendered).not_to have_text(first_message.body)
+      expect(rendered).to have_text(last_message.body)
+    end
+  end
 end