diff --git a/crypto/codec/tm.go b/crypto/codec/tm.go
index 6633f60c2377..8c841e96b3c7 100644
--- a/crypto/codec/tm.go
+++ b/crypto/codec/tm.go
@@ -6,6 +6,7 @@ import (
 	tmprotocrypto "github.com/tendermint/tendermint/proto/tendermint/crypto"
 
 	"github.com/cosmos/cosmos-sdk/crypto/keys/ed25519"
+	"github.com/cosmos/cosmos-sdk/crypto/keys/secp256k1"
 	cryptotypes "github.com/cosmos/cosmos-sdk/crypto/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 )
@@ -17,6 +18,10 @@ func FromTmProtoPublicKey(protoPk tmprotocrypto.PublicKey) (cryptotypes.PubKey,
 		return &ed25519.PubKey{
 			Key: protoPk.Ed25519,
 		}, nil
+	case *tmprotocrypto.PublicKey_Secp256K1:
+		return &secp256k1.PubKey{
+			Key: protoPk.Secp256K1,
+		}, nil
 	default:
 		return nil, sdkerrors.Wrapf(sdkerrors.ErrInvalidType, "cannot convert %v from Tendermint public key", protoPk)
 	}
@@ -31,6 +36,12 @@ func ToTmProtoPublicKey(pk cryptotypes.PubKey) (tmprotocrypto.PublicKey, error)
 				Ed25519: pk.Key,
 			},
 		}, nil
+	case *secp256k1.PubKey:
+		return tmprotocrypto.PublicKey{
+			Sum: &tmprotocrypto.PublicKey_Secp256K1{
+				Secp256K1: pk.Key,
+			},
+		}, nil
 	default:
 		return tmprotocrypto.PublicKey{}, sdkerrors.Wrapf(sdkerrors.ErrInvalidType, "cannot convert %v to Tendermint public key", pk)
 	}
diff --git a/crypto/keys/secp256k1/secp256k1_test.go b/crypto/keys/secp256k1/secp256k1_test.go
index d96b1dc38216..56c67f594b0b 100644
--- a/crypto/keys/secp256k1/secp256k1_test.go
+++ b/crypto/keys/secp256k1/secp256k1_test.go
@@ -12,6 +12,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/tendermint/tendermint/crypto"
+	tmsecp256k1 "github.com/tendermint/tendermint/crypto/secp256k1"
 
 	"github.com/cosmos/cosmos-sdk/codec"
 	"github.com/cosmos/cosmos-sdk/crypto/keys/ed25519"
@@ -267,3 +268,56 @@ func TestMarshalAmino(t *testing.T) {
 		})
 	}
 }
+
+func TestMarshalAmino_BackwardsCompatibility(t *testing.T) {
+	aminoCdc := codec.NewLegacyAmino()
+	// Create Tendermint keys.
+	tmPrivKey := tmsecp256k1.GenPrivKey()
+	tmPubKey := tmPrivKey.PubKey()
+	// Create our own keys, with the same private key as Tendermint's.
+	privKey := &secp256k1.PrivKey{Key: []byte(tmPrivKey)}
+	pubKey := privKey.PubKey().(*secp256k1.PubKey)
+
+	testCases := []struct {
+		desc      string
+		tmKey     interface{}
+		ourKey    interface{}
+		marshalFn func(o interface{}) ([]byte, error)
+	}{
+		{
+			"secp256k1 private key, binary",
+			tmPrivKey,
+			privKey,
+			aminoCdc.MarshalBinaryBare,
+		},
+		{
+			"secp256k1 private key, JSON",
+			tmPrivKey,
+			privKey,
+			aminoCdc.MarshalJSON,
+		},
+		{
+			"secp256k1 public key, binary",
+			tmPubKey,
+			pubKey,
+			aminoCdc.MarshalBinaryBare,
+		},
+		{
+			"secp256k1 public key, JSON",
+			tmPubKey,
+			pubKey,
+			aminoCdc.MarshalJSON,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(t *testing.T) {
+			// Make sure Amino encoding override is not breaking backwards compatibility.
+			bz1, err := tc.marshalFn(tc.tmKey)
+			require.NoError(t, err)
+			bz2, err := tc.marshalFn(tc.ourKey)
+			require.NoError(t, err)
+			require.Equal(t, bz1, bz2)
+		})
+	}
+}
diff --git a/x/staking/handler_test.go b/x/staking/handler_test.go
index 844fc779905b..c3bcc8ea3350 100644
--- a/x/staking/handler_test.go
+++ b/x/staking/handler_test.go
@@ -12,7 +12,9 @@ import (
 	tmtypes "github.com/tendermint/tendermint/types"
 
 	cryptocodec "github.com/cosmos/cosmos-sdk/crypto/codec"
+	"github.com/cosmos/cosmos-sdk/crypto/keys/ed25519"
 	"github.com/cosmos/cosmos-sdk/crypto/keys/secp256k1"
+	cryptotypes "github.com/cosmos/cosmos-sdk/crypto/types"
 	"github.com/cosmos/cosmos-sdk/simapp"
 	"github.com/cosmos/cosmos-sdk/testutil/testdata"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -181,6 +183,37 @@ func TestInvalidPubKeyTypeMsgCreateValidator(t *testing.T) {
 	tstaking.CreateValidator(addr, invalidPk, 10, false)
 }
 
+func TestBothPubKeyTypesMsgCreateValidator(t *testing.T) {
+	app, ctx, _, valAddrs := bootstrapHandlerGenesisTest(t, 1000, 2, 1000)
+	ctx = ctx.WithConsensusParams(&abci.ConsensusParams{
+		Validator: &tmproto.ValidatorParams{PubKeyTypes: []string{tmtypes.ABCIPubKeyTypeEd25519, tmtypes.ABCIPubKeyTypeSecp256k1}},
+	})
+
+	tstaking := teststaking.NewHelper(t, ctx, app.StakingKeeper)
+
+	testCases := []struct {
+		name string
+		addr sdk.ValAddress
+		pk   cryptotypes.PubKey
+	}{
+		{
+			"can create a validator with ed25519 pubkey",
+			valAddrs[0],
+			ed25519.GenPrivKey().PubKey(),
+		},
+		{
+			"can create a validator with secp256k1 pubkey",
+			valAddrs[1],
+			secp256k1.GenPrivKey().PubKey(),
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(*testing.T) {
+			tstaking.CreateValidator(tc.addr, tc.pk, 10, true)
+		})
+	}
+}
+
 func TestLegacyValidatorDelegations(t *testing.T) {
 	app, ctx, delAddrs, valAddrs := bootstrapHandlerGenesisTest(t, 1000, 2, 100000000)