diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7dcf22728d..b9cc99f776 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,8 @@
 # Changelog
 
-## vNext
+## Unreleased
 
+- Handle non-json error response messages on HttpTransport. (#690) @lucas-zimerman
 - Fix deadlock on missing ConfigureAwait into foreach loops. (#694) @lucas-zimerman
 
 ## 3.0.0-alpha.8
diff --git a/src/Sentry/Internal/Http/HttpTransport.cs b/src/Sentry/Internal/Http/HttpTransport.cs
index 8c90213608..a0144d286f 100644
--- a/src/Sentry/Internal/Http/HttpTransport.cs
+++ b/src/Sentry/Internal/Http/HttpTransport.cs
@@ -111,25 +111,41 @@ public async Task SendEnvelopeAsync(Envelope envelope, CancellationToken cancell
             }
             else if (_options.DiagnosticLogger?.IsEnabled(SentryLevel.Error) == true)
             {
-                var responseJson = await response.Content.ReadAsJsonAsync(cancellationToken).ConfigureAwait(false);
-
-                var errorMessage =
-                    responseJson.GetPropertyOrNull("detail")?.GetString()
-                    ?? DefaultErrorMessage;
-
-                var errorCauses =
-                    responseJson.GetPropertyOrNull("causes")?.EnumerateArray().Select(j => j.GetString()).ToArray()
-                    ?? Array.Empty<string>();
-
-                _options.DiagnosticLogger?.Log(
-                    SentryLevel.Error,
-                    "Sentry rejected the envelope {0}. Status code: {1}. Error detail: {2}. Error causes: {3}.",
-                    null,
-                    processedEnvelope.TryGetEventId(),
-                    response.StatusCode,
-                    errorMessage,
-                    string.Join(", ", errorCauses)
-                );
+                if (response.Content.Headers.ContentType?.MediaType is "application/json")
+                {
+                    var responseJson = await response.Content.ReadAsJsonAsync(cancellationToken).ConfigureAwait(false);
+
+                    var errorMessage =
+                        responseJson.GetPropertyOrNull("detail")?.GetString()
+                        ?? DefaultErrorMessage;
+
+                    var errorCauses =
+                        responseJson.GetPropertyOrNull("causes")?.EnumerateArray().Select(j => j.GetString()).ToArray()
+                        ?? Array.Empty<string>();
+
+                    _options.DiagnosticLogger?.Log(
+                        SentryLevel.Error,
+                        "Sentry rejected the envelope {0}. Status code: {1}. Error detail: {2}. Error causes: {3}.",
+                        null,
+                        processedEnvelope.TryGetEventId(),
+                        response.StatusCode,
+                        errorMessage,
+                        string.Join(", ", errorCauses)
+                    );
+                }
+                else
+                {
+                    var responseString = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
+
+                    _options.DiagnosticLogger?.Log(
+                        SentryLevel.Error,
+                        "Sentry rejected the envelope {0}. Status code: {1}. Error detail: {2}.",
+                        null,
+                        processedEnvelope.TryGetEventId(),
+                        response.StatusCode,
+                        responseString
+                    );
+                }
             }
         }
 
diff --git a/test/Sentry.Testing/SentryResponses.cs b/test/Sentry.Testing/SentryResponses.cs
index 9a63f54dee..59368c19c8 100644
--- a/test/Sentry.Testing/SentryResponses.cs
+++ b/test/Sentry.Testing/SentryResponses.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Net;
 using System.Net.Http;
+using System.Text;
 using System.Text.Json;
 
 namespace Sentry.Testing
@@ -20,15 +21,21 @@ public static HttpResponseMessage GetOkResponse()
                 Content = GetOkContent()
             };
 
-        public static HttpResponseMessage GetErrorResponse(HttpStatusCode code, string detail, string[] causes = null)
+        public static HttpResponseMessage GetJsonErrorResponse(HttpStatusCode code, string detail, string[] causes = null)
         {
             var responseContent = causes != null
                 ? JsonSerializer.Serialize(new {detail, causes})
                 : JsonSerializer.Serialize(new {detail});
 
-            return new HttpResponseMessage(code) {Content = new StringContent(responseContent)};
+            return new HttpResponseMessage(code) {Content = new StringContent(responseContent, Encoding.UTF8, "application/json") };
         }
 
+        public static HttpResponseMessage GetTextErrorResponse(HttpStatusCode code, string detail)
+            => new HttpResponseMessage(code)
+            {
+                Content = new StringContent(detail)
+            };
+
         public static HttpResponseMessage GetRateLimitResponse(string rateLimitHeaderValue)
         {
             return new((HttpStatusCode)429)
diff --git a/test/Sentry.Tests/Internals/Http/HttpTransportTests.cs b/test/Sentry.Tests/Internals/Http/HttpTransportTests.cs
index def15ad573..b0d461a238 100644
--- a/test/Sentry.Tests/Internals/Http/HttpTransportTests.cs
+++ b/test/Sentry.Tests/Internals/Http/HttpTransportTests.cs
@@ -52,7 +52,7 @@ await httpHandler
         }
 
         [Fact]
-        public async Task SendEnvelopeAsync_ResponseNotOkWithMessage_LogsError()
+        public async Task SendEnvelopeAsync_ResponseNotOkWithJsonMessage_LogsError()
         {
             // Arrange
             const HttpStatusCode expectedCode = HttpStatusCode.BadGateway;
@@ -63,7 +63,7 @@ public async Task SendEnvelopeAsync_ResponseNotOkWithMessage_LogsError()
             var httpHandler = Substitute.For<MockableHttpMessageHandler>();
 
             httpHandler.VerifiableSendAsync(Arg.Any<HttpRequestMessage>(), Arg.Any<CancellationToken>())
-                .Returns(_ => SentryResponses.GetErrorResponse(expectedCode, expectedMessage, expectedCauses));
+                .Returns(_ => SentryResponses.GetJsonErrorResponse(expectedCode, expectedMessage, expectedCauses));
 
             var logger = new AccumulativeDiagnosticLogger();
 
@@ -94,6 +94,46 @@ public async Task SendEnvelopeAsync_ResponseNotOkWithMessage_LogsError()
             ).Should().BeTrue();
         }
 
+        [Fact]
+        public async Task SendEnvelopeAsync_ResponseNotOkWithStringMessage_LogsError()
+        {
+            // Arrange
+            const HttpStatusCode expectedCode = HttpStatusCode.RequestEntityTooLarge;
+            const string expectedMessage = "413 Request Entity Too Large";
+
+            var httpHandler = Substitute.For<MockableHttpMessageHandler>();
+
+            _ = httpHandler.VerifiableSendAsync(Arg.Any<HttpRequestMessage>(), Arg.Any<CancellationToken>())
+                  .Returns(_ => SentryResponses.GetTextErrorResponse(expectedCode, expectedMessage));
+
+            var logger = new AccumulativeDiagnosticLogger();
+
+            var httpTransport = new HttpTransport(
+                new SentryOptions
+                {
+                    Dsn = DsnSamples.ValidDsnWithSecret,
+                    Debug = true,
+                    DiagnosticLogger = logger
+                },
+                new HttpClient(httpHandler)
+            );
+
+            var envelope = Envelope.FromEvent(new SentryEvent());
+
+            // Act
+            await httpTransport.SendEnvelopeAsync(envelope);
+
+            // Assert
+            _ = logger.Entries.Any(e =>
+                    e.Level == SentryLevel.Error &&
+                    e.Message == "Sentry rejected the envelope {0}. Status code: {1}. Error detail: {2}." &&
+                    e.Exception == null &&
+                    e.Args[0].ToString() == envelope.TryGetEventId().ToString() &&
+                    e.Args[1].ToString() == expectedCode.ToString() &&
+                    e.Args[2].ToString() == expectedMessage
+            ).Should().BeTrue();
+        }
+
         [Fact]
         public async Task SendEnvelopeAsync_ResponseNotOkNoMessage_LogsError()
         {
@@ -103,7 +143,7 @@ public async Task SendEnvelopeAsync_ResponseNotOkNoMessage_LogsError()
             var httpHandler = Substitute.For<MockableHttpMessageHandler>();
 
             httpHandler.VerifiableSendAsync(Arg.Any<HttpRequestMessage>(), Arg.Any<CancellationToken>())
-                .Returns(_ => SentryResponses.GetErrorResponse(expectedCode, null));
+                .Returns(_ => SentryResponses.GetJsonErrorResponse(expectedCode, null));
 
             var logger = new AccumulativeDiagnosticLogger();