diff --git a/listenarr.application/Search/Metadata/MetadataConverters.cs b/listenarr.application/Search/Metadata/MetadataConverters.cs
index b70e2b443..a319df931 100644
--- a/listenarr.application/Search/Metadata/MetadataConverters.cs
+++ b/listenarr.application/Search/Metadata/MetadataConverters.cs
@@ -143,6 +143,7 @@ public AudibleBookMetadata ConvertAudnexusToMetadata(AudnexusBookResponse audnex
         {
             audnexusSeriesMemberships.Add(new AudiobookSeriesMembership
             {
+                SeriesAsin = audnexusData.SeriesPrimary.Asin,
                 SeriesName = audnexusData.SeriesPrimary.Name,
                 SeriesNumber = audnexusData.SeriesPrimary.Position,
                 IsPrimary = true,
@@ -154,6 +155,7 @@ public AudibleBookMetadata ConvertAudnexusToMetadata(AudnexusBookResponse audnex
         {
             audnexusSeriesMemberships.Add(new AudiobookSeriesMembership
             {
+                SeriesAsin = audnexusData.SeriesSecondary.Asin,
                 SeriesName = audnexusData.SeriesSecondary.Name,
                 SeriesNumber = audnexusData.SeriesSecondary.Position,
                 IsPrimary = audnexusSeriesMemberships.Count == 0,
diff --git a/tests/Features/Application/Search/Metadata/MetadataConvertersSeriesAsinTests.cs b/tests/Features/Application/Search/Metadata/MetadataConvertersSeriesAsinTests.cs
new file mode 100644
index 000000000..1919b8f0f
--- /dev/null
+++ b/tests/Features/Application/Search/Metadata/MetadataConvertersSeriesAsinTests.cs
@@ -0,0 +1,95 @@
+/*
+ * Listenarr - Audiobook Management System
+ * Copyright (C) 2024-2026 Listenarr Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+using Listenarr.Application.Metadata.Audnexus;
+using Listenarr.Application.Search.Metadata;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace Listenarr.Tests.Features.Application.Search.Metadata
+{
+    /// <summary>
+    /// Audnexus returns an ASIN for each series a book belongs to, and
+    /// AudiobookSeriesMembership has a SeriesAsin column to hold it. The converter maps the
+    /// series name and position but drops the ASIN, so SeriesAsin is never populated.
+    ///
+    /// The series ASIN is the stable identifier: a book ASIN is per-marketplace and
+    /// per-narrator, and a series name is free text that varies between editions.
+    ///
+    /// Data below is from the live Audnexus record for H. Rider Haggard's "She and Allan"
+    /// (B00CQ5WAXW), which belongs to two series at once.
+    /// </summary>
+    public class MetadataConvertersSeriesAsinTests
+    {
+        private static MetadataConverters Converter() =>
+            new(imageCacheService: null,
+                NullLogger<MetadataConverters>.Instance,
+                requestContextAccessor: null);
+
+        private static AudnexusBookResponse SheAndAllan() => new()
+        {
+            Asin = "B00CQ5WAXW",
+            Title = "She and Allan",
+            SeriesPrimary = new AudnexusSeries
+            {
+                Asin = "B01E633FQM",
+                Name = "Ayesha",
+                Position = "0",
+            },
+            SeriesSecondary = new AudnexusSeries
+            {
+                Asin = "B01F5TL5K4",
+                Name = "Allan Quatermain",
+                Position = "7",
+            },
+        };
+
+        [Fact]
+        public void PrimarySeriesAsin_IsMapped()
+        {
+            var metadata = Converter().ConvertAudnexusToMetadata(SheAndAllan(), "B00CQ5WAXW");
+
+            var primary = metadata.SeriesMemberships?.Single(m => m.IsPrimary);
+
+            Assert.NotNull(primary);
+            Assert.Equal("Ayesha", primary!.SeriesName);
+            Assert.Equal("0", primary.SeriesNumber);
+            Assert.Equal("B01E633FQM", primary.SeriesAsin);
+        }
+
+        [Fact]
+        public void SecondarySeriesAsin_IsMapped()
+        {
+            var metadata = Converter().ConvertAudnexusToMetadata(SheAndAllan(), "B00CQ5WAXW");
+
+            var secondary = metadata.SeriesMemberships?.Single(m => !m.IsPrimary);
+
+            Assert.NotNull(secondary);
+            Assert.Equal("Allan Quatermain", secondary!.SeriesName);
+            Assert.Equal("7", secondary.SeriesNumber);
+            Assert.Equal("B01F5TL5K4", secondary.SeriesAsin);
+        }
+
+        [Fact]
+        public void ABookInTwoSeries_KeepsBothMemberships()
+        {
+            var metadata = Converter().ConvertAudnexusToMetadata(SheAndAllan(), "B00CQ5WAXW");
+
+            Assert.Equal(2, metadata.SeriesMemberships?.Count);
+        }
+    }
+}