diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Revision history for either-result
 
+## 0.3.1.0
+
+*2020.08.16*
+
+- Add mtl instances
+
 ## 0.3.0.0
 
 *2020.08.05*
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 # either-result
 
-[![Hackage](https://matrix.hackage.haskell.org/api/v2/packages/either-result/badge)](http://hackage.haskell.org/package/either-result) [![GitHub Actions: lint](https://github.com/kakkun61/either-result/workflows/test/badge.svg)](https://github.com/kakkun61/either-result/actions?query=workflow%3Atest) [![GitHub Actions: lint](https://github.com/kakkun61/either-result/workflows/lint/badge.svg)](https://github.com/kakkun61/either-result/actions?query=workflow%3Alint) [![Join the chat at https://gitter.im/either-result/community](https://badges.gitter.im/either-result/community.svg)](https://gitter.im/either-result/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Sponsor](https://img.shields.io/badge/Sponsor-%E2%9D%A4-red?logo=GitHub)](https://github.com/sponsors/kakkun61)
+[![Hackage](https://matrix.hackage.haskell.org/api/v2/packages/either-result/badge)](http://hackage.haskell.org/package/either-result) [![GitHub Actions: test](https://github.com/kakkun61/either-result/workflows/test/badge.svg)](https://github.com/kakkun61/either-result/actions?query=workflow%3Atest) [![GitHub Actions: lint](https://github.com/kakkun61/either-result/workflows/lint/badge.svg)](https://github.com/kakkun61/either-result/actions?query=workflow%3Alint) [![Join the chat at https://gitter.im/either-result/community](https://badges.gitter.im/either-result/community.svg)](https://gitter.im/either-result/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Sponsor](https://img.shields.io/badge/Sponsor-%E2%9D%A4-red?logo=GitHub)](https://github.com/sponsors/kakkun61)
 
 `Result a` is a wrapper of `Either String a`, but `Result` is an instance of `MonadFail`.
diff --git a/either-result.cabal b/either-result.cabal
--- a/either-result.cabal
+++ b/either-result.cabal
@@ -1,7 +1,7 @@
 cabal-version: 2.2
 
 name: either-result
-version: 0.3.0.0
+version: 0.3.1.0
 synopsis: ‘MonadFail’ instance for a wrapper of ‘ExceptT String m a’.
 description: ‘ResultT m a’ is a wrapper of ‘ExceptT String m a’ which are similar except ‘MonadFail’ instance.
 homepage: https://github.com/kakkun61/either-result
diff --git a/src/Control/Monad/Trans/Except/Result.hs b/src/Control/Monad/Trans/Except/Result.hs
--- a/src/Control/Monad/Trans/Except/Result.hs
+++ b/src/Control/Monad/Trans/Except/Result.hs
@@ -34,8 +34,13 @@
 
 import Control.Applicative        (Alternative)
 import Control.Monad              (MonadPlus)
+import Control.Monad.Cont.Class   (MonadCont)
 import Control.Monad.Fix          (MonadFix)
 import Control.Monad.IO.Class     (MonadIO)
+import Control.Monad.Reader.Class (MonadReader)
+import Control.Monad.RWS.Class    (MonadRWS)
+import Control.Monad.State.Class  (MonadState)
+import Control.Monad.Writer.Class (MonadWriter)
 import Control.Monad.Zip          (MonadZip)
 import Data.Functor.Classes       (Eq1, Ord1, Read1 (liftReadPrec), Show1 (liftShowsPrec), readData, readUnaryWith,
                                    showsUnaryWith)
@@ -70,7 +75,7 @@
       runResultT :: ExceptT String m a
     }
   deriving stock (Show, Read, Eq, Ord, Generic, Functor, Foldable, Traversable)
-  deriving newtype (Eq1, Ord1, Applicative, Alternative, Monad, MonadTrans, MonadFix, MonadZip, MonadIO, MonadPlus, Contravariant)
+  deriving newtype (Eq1, Ord1, Applicative, Alternative, Monad, MonadTrans, MonadFix, MonadZip, MonadIO, MonadPlus, MonadCont, MonadRWS r w s, MonadReader r, MonadState s, MonadWriter w, Contravariant)
 
 instance Read1 m => Read1 (ResultT m) where
   liftReadPrec rp rl =
diff --git a/src/Control/Monad/Trans/Result.hs b/src/Control/Monad/Trans/Result.hs
--- a/src/Control/Monad/Trans/Result.hs
+++ b/src/Control/Monad/Trans/Result.hs
@@ -1,8 +1,8 @@
-{-# LANGUAGE CPP                  #-}
-{-# LANGUAGE ExplicitNamespaces   #-}
-{-# LANGUAGE FlexibleInstances    #-}
-{-# LANGUAGE PatternSynonyms      #-}
-{-# LANGUAGE ViewPatterns         #-}
+{-# LANGUAGE CPP                #-}
+{-# LANGUAGE ExplicitNamespaces #-}
+{-# LANGUAGE FlexibleInstances  #-}
+{-# LANGUAGE PatternSynonyms    #-}
+{-# LANGUAGE ViewPatterns       #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}