diff --git a/src/Todoist.Net.Tests/RateLimitAwareRestClient.cs b/src/Todoist.Net.Tests/RateLimitAwareRestClient.cs
index 523ebac..9435c37 100644
--- a/src/Todoist.Net.Tests/RateLimitAwareRestClient.cs
+++ b/src/Todoist.Net.Tests/RateLimitAwareRestClient.cs
@@ -80,6 +80,15 @@ public async Task<HttpResponseMessage> PostFormAsync(
                        .ConfigureAwait(false);
         }
 
+        public async Task<HttpResponseMessage> PostFormAsync(
+            string resource,
+            MultipartFormDataContent data,
+            CancellationToken cancellationToken = default)
+        {
+            return await ExecuteRequest(() => _restClient.PostFormAsync(resource, data, cancellationToken))
+                .ConfigureAwait(false);
+        }
+
         public async Task<TimeSpan> GetRateLimitCooldown(HttpResponseMessage response)
         {
             var defaultCooldown = TimeSpan.FromSeconds(30);
diff --git a/src/Todoist.Net/IAdvancedTodoistClient.cs b/src/Todoist.Net/IAdvancedTodoistClient.cs
index 287a3ce..b2d094e 100644
--- a/src/Todoist.Net/IAdvancedTodoistClient.cs
+++ b/src/Todoist.Net/IAdvancedTodoistClient.cs
@@ -83,6 +83,24 @@ Task<T> PostFormAsync<T>(
             IEnumerable<ByteArrayContent> files,
             CancellationToken cancellationToken = default);
 
+        /// <summary>
+        /// Sends a <c>POST</c> request with form data, and handles response asynchronously.
+        /// </summary>
+        /// <typeparam name="T">The result type.</typeparam>
+        /// <param name="resource">The resource.</param>
+        /// <param name="parameters">The parameters.</param>
+        /// <param name="files">The files.</param>
+        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
+        /// <returns>
+        /// The result.
+        /// </returns>
+        /// <exception cref="HttpRequestException">API exception.</exception>
+        Task<T> PostFormAsync<T>(
+            string resource,
+            ICollection<KeyValuePair<string, string>> parameters,
+            IEnumerable<FormFile> files,
+            CancellationToken cancellationToken = default);
+
         /// <summary>
         /// Sends a <c>POST</c> request asynchronously, and returns raw content.
         /// </summary>
diff --git a/src/Todoist.Net/ITodoistRestClient.cs b/src/Todoist.Net/ITodoistRestClient.cs
index 2920e9e..7bdeec9 100644
--- a/src/Todoist.Net/ITodoistRestClient.cs
+++ b/src/Todoist.Net/ITodoistRestClient.cs
@@ -45,6 +45,20 @@ Task<HttpResponseMessage> PostFormAsync(
             string resource,
             IEnumerable<KeyValuePair<string, string>> parameters,
             IEnumerable<ByteArrayContent> files,
-            CancellationToken cancellationToken = default);
+            CancellationToken cancellationToken = default
+        );
+
+        /// <summary>
+        /// Sends a <c>POST</c> request with form data, and handles response asynchronously.
+        /// </summary>
+        /// <param name="resource">The resource.</param>
+        /// <param name="data">The form data.</param>
+        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
+        /// <returns>The response.</returns>
+        Task<HttpResponseMessage> PostFormAsync(
+            string resource,
+            MultipartFormDataContent data,
+            CancellationToken cancellationToken = default
+        );
     }
 }
diff --git a/src/Todoist.Net/Models/FormFile.cs b/src/Todoist.Net/Models/FormFile.cs
new file mode 100644
index 0000000..899cb49
--- /dev/null
+++ b/src/Todoist.Net/Models/FormFile.cs
@@ -0,0 +1,16 @@
+namespace Todoist.Net.Models
+{
+    internal class FormFile
+    {
+        public FormFile(byte[] content, string filename, string mimeType = null)
+        {
+            Content  = content;
+            Filename = filename;
+            MimeType = mimeType;
+        }
+
+        public byte[] Content;
+        public string Filename;
+        public string MimeType;
+    }
+}
diff --git a/src/Todoist.Net/Services/UploadService.cs b/src/Todoist.Net/Services/UploadService.cs
index be68d13..f73d599 100644
--- a/src/Todoist.Net/Services/UploadService.cs
+++ b/src/Todoist.Net/Services/UploadService.cs
@@ -1,8 +1,15 @@
 using System.Collections.Generic;
 using System.Net.Http;
+using System.Net.Http.Headers;
 using System.Threading;
 using System.Threading.Tasks;
 
+#if NETSTANDARD2_0
+using Microsoft.AspNetCore.StaticFiles;
+#else
+using System.Web;
+#endif
+
 using Todoist.Net.Models;
 
 namespace Todoist.Net.Services
@@ -15,6 +22,10 @@ internal class UploadService : IUploadService
     {
         private readonly IAdvancedTodoistClient _todoistClient;
 
+        #if NETSTANDARD2_0
+        private static readonly FileExtensionContentTypeProvider MimeProvider = new FileExtensionContentTypeProvider();
+        #endif
+
         internal UploadService(IAdvancedTodoistClient todoistClient)
         {
             _todoistClient = todoistClient;
@@ -40,13 +51,19 @@ public Task<IEnumerable<Upload>> GetAsync(CancellationToken cancellationToken =
         }
 
         /// <inheritdoc/>
-        public Task<FileAttachment> UploadAsync(string fileName, byte[] fileContent, CancellationToken cancellationToken = default)
+        public Task<FileAttachment> UploadAsync(
+            string fileName, byte[] fileContent, CancellationToken cancellationToken = default
+        )
         {
-            var parameters = new List<KeyValuePair<string, string>>
-                                 {
-                                     new KeyValuePair<string, string>("file_name", fileName)
-                                 };
-            var files = new[] { new ByteArrayContent(fileContent) };
+#if NETSTANDARD2_0
+            MimeProvider.TryGetContentType(fileName, out var mimeType);
+#else
+            var mimeType = MimeMapping.GetMimeMapping(fileName);
+#endif
+
+            var parameters = new Dictionary<string, string>();
+            var file = new FormFile(fileContent, fileName, mimeType);
+            var files = new[] { file };
 
             return _todoistClient.PostFormAsync<FileAttachment>("uploads/add", parameters, files, cancellationToken);
         }
diff --git a/src/Todoist.Net/Todoist.Net.csproj b/src/Todoist.Net/Todoist.Net.csproj
index 5fbc95c..ada5275 100644
--- a/src/Todoist.Net/Todoist.Net.csproj
+++ b/src/Todoist.Net/Todoist.Net.csproj
@@ -31,6 +31,7 @@
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
     <Reference Include="System.Net.Http" />
+    <Reference Include="System.Web" />
   </ItemGroup>
 
   <ItemGroup>
@@ -46,6 +47,7 @@
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
     <PackageReference Include="Microsoft.Extensions.Http" Version="6.0.1" />
+    <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="2.3.0" />
   </ItemGroup>
 
 </Project>
diff --git a/src/Todoist.Net/TodoistClient.cs b/src/Todoist.Net/TodoistClient.cs
index c563a21..6fad1be 100644
--- a/src/Todoist.Net/TodoistClient.cs
+++ b/src/Todoist.Net/TodoistClient.cs
@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Net;
 using System.Net.Http;
+using System.Net.Http.Headers;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using System.Text.Json.Serialization.Metadata;
@@ -298,6 +299,30 @@ Task<T> IAdvancedTodoistClient.PostFormAsync<T>(
             return ProcessFormAsync<T>(resource, parameters, files, cancellationToken);
         }
 
+        /// <inheritdoc/>
+        Task<T> IAdvancedTodoistClient.PostFormAsync<T>(
+            string resource,
+            ICollection<KeyValuePair<string, string>> parameters,
+            IEnumerable<FormFile> files,
+            CancellationToken cancellationToken)
+        {
+            var data = new MultipartFormDataContent();
+
+            foreach (var file in files)
+            {
+                var mime    = file.MimeType != null ? MediaTypeHeaderValue.Parse(file.MimeType) : null;
+                var content = new ByteArrayContent(file.Content) { Headers = { ContentType = mime } };
+                data.Add(content, "file", file.Filename);
+            }
+
+            foreach (var keyValuePair in parameters)
+            {
+                data.Add(new StringContent(keyValuePair.Value), $"\"{keyValuePair.Key}\"");
+            }
+
+            return ProcessFormAsync<T>(resource, data, cancellationToken);
+        }
+
         /// <inheritdoc/>
         async Task<T> IAdvancedTodoistClient.GetAsync<T>(
             string resource,
@@ -357,6 +382,29 @@ private async Task<T> ProcessFormAsync<T>(
             return DeserializeResponse<T>(responseContent);
         }
 
+        /// <summary>
+        /// Processes the form asynchronous.
+        /// </summary>
+        /// <typeparam name="T">The type of the response.</typeparam>
+        /// <param name="resource">The resource.</param>
+        /// <param name="data">The form data.</param>
+        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
+        /// <exception cref="HttpRequestException">API exception.</exception>
+        /// <returns>The response.</returns>
+        private async Task<T> ProcessFormAsync<T>(
+            string resource,
+            MultipartFormDataContent data,
+            CancellationToken cancellationToken)
+        {
+            var response = await _restClient.PostFormAsync(resource, data, cancellationToken).ConfigureAwait(false);
+
+            var responseContent = await ReadResponseAsync(response, cancellationToken)
+                .ConfigureAwait(false);
+
+            return DeserializeResponse<T>(responseContent);
+        }
+
+
         /// <summary>
         /// Processes the request asynchronous.
         /// </summary>
diff --git a/src/Todoist.Net/TodoistRestClient.cs b/src/Todoist.Net/TodoistRestClient.cs
index 9a80442..c9725af 100644
--- a/src/Todoist.Net/TodoistRestClient.cs
+++ b/src/Todoist.Net/TodoistRestClient.cs
@@ -63,7 +63,7 @@ public void Dispose()
         {
             if (_disposeHttpClient)
             {
-                _httpClient?.Dispose(); 
+                _httpClient?.Dispose();
             }
         }
 
@@ -134,8 +134,19 @@ public async Task<HttpResponseMessage> PostFormAsync(
                     multipartFormDataContent.Add(file, Guid.NewGuid().ToString(), Guid.NewGuid().ToString());
                 }
 
-                return await _httpClient.PostAsync(resource, multipartFormDataContent, cancellationToken).ConfigureAwait(false);
+                return await _httpClient.PostAsync(resource, multipartFormDataContent, cancellationToken)
+                                        .ConfigureAwait(false);
             }
         }
+
+        /// <inheritdoc/>
+        public async Task<HttpResponseMessage> PostFormAsync(
+            string resource,
+            MultipartFormDataContent data,
+            CancellationToken cancellationToken = default
+        )
+        {
+            return await _httpClient.PostAsync(resource, data, cancellationToken).ConfigureAwait(false);
+        }
     }
 }