diff --git a/core/themes/seven/dialog.theme.css b/core/themes/seven/dialog.theme.css
new file mode 100644
index 0000000..c569785
--- /dev/null
+++ b/core/themes/seven/dialog.theme.css
@@ -0,0 +1,83 @@
+/**
+ * Presentational styles for Drupal dialogs.
+ */
+
+.ui-dialog {
+  background: transparent;
+  border: 0;
+  position: absolute;
+  z-index: 1260;
+  overflow: visible;
+  padding: 0;
+}
+.ui-dialog .ui-dialog-titlebar {
+  background: rgba(107,107,107,0.65);
+  border-top-left-radius: 5px;
+  border-top-right-radius: 5px;
+  padding: 20px;
+}
+.ui-dialog .ui-dialog-title {
+  font-size: 22px;
+  font-weight: 600;
+  margin: 0;
+  color: #ffffff;
+  -webkit-font-smoothing: antialiased;
+}
+.ui-dialog .ui-dialog-titlebar-close {
+  border: 0;
+  background: none;
+  right: 20px;
+  top: 20px;
+  margin: 0;
+  height: 16px;
+  width: 16px;
+}
+.ui-dialog .ui-icon-closethick {
+  background: url('../../misc/icons/ffffff/ex.svg') 0 0 no-repeat;
+}
+.ui-dialog .ui-dialog-content {
+  background: #ffffff;
+}
+.ui-dialog .ui-dialog-buttonpane {
+  background: #f5f5f2;
+  border-top: 1px solid #bfbfbf;
+  margin: 0;
+  padding: 15px 20px;
+  border-bottom-left-radius: 5px;
+  border-bottom-right-radius: 5px;
+}
+.ui-dialog .ui-dialog-buttonpane .ui-dialog-buttonset {
+  margin: 0;
+  padding: 0;
+  float: none;
+}
+.ui-dialog .ui-dialog-buttonpane .ui-button-text-only .ui-button-text {
+  padding: 0;
+}
+
+/* Form action buttons are moved in dialogs. Remove empty space. */
+.ui-dialog .ui-dialog-content .form-actions {
+  padding: 0;
+  margin: 0;
+}
+.ui-dialog .ajax-progress-throbber {
+  /* Can't do center:50% middle: 50%, so approximate it for a typical window size. */
+  left: 49%;
+  position: fixed;
+  top: 48.5%;
+  z-index: 1000;
+  background-color: #232323;
+  background-image: url("loading-small.gif");
+  background-position: center center;
+  background-repeat: no-repeat;
+  border-radius: 7px;
+  height: 24px;
+  opacity: 0.9;
+  padding: 4px;
+  width: 24px;
+}
+.ui-dialog .ajax-progress-throbber .throbber,
+.ui-dialog .ajax-progress-throbber .message {
+  display: none;
+}
+
diff --git a/core/themes/seven/seven.info.yml b/core/themes/seven/seven.info.yml
index c7f80bb..80ba1f5 100644
--- a/core/themes/seven/seven.info.yml
+++ b/core/themes/seven/seven.info.yml
@@ -10,6 +10,7 @@ stylesheets:
 stylesheets-override:
   - vertical-tabs.css
   - jquery.ui.theme.css
+  - dialog.theme.css
 edit_stylesheets:
   - edit.css
 settings: