diff --git a/ccip/config/evm/Sei_Testnet_Atlantic.toml b/ccip/config/evm/Sei_Testnet_Atlantic.toml
new file mode 100644
index 0000000000..e595c2dcdf
--- /dev/null
+++ b/ccip/config/evm/Sei_Testnet_Atlantic.toml
@@ -0,0 +1,17 @@
+ChainID = '1328'
+ChainType = 'sei'
+# finality_depth: instant
+FinalityDepth = 10
+# block_time: ~0.4s, adding 1 second buffer
+LogPollInterval = '2s'
+# finality_depth * block_time / 60 secs = ~0.8 min (finality time)
+NoNewFinalizedHeadsThreshold = '5m'
+# "RPC node returned multiple missing blocks on query for block numbers [31592085 31592084] even though the WS subscription already sent us these blocks. It might help to increase EVM.RPCBlockQueryDelay (currently 1)"
+RPCBlockQueryDelay = 5 
+
+[GasEstimator]
+EIP1559DynamicFees = false
+Mode = 'BlockHistory'
+
+[GasEstimator.BlockHistory]
+BlockHistorySize = 200
diff --git a/core/chains/evm/client/errors.go b/core/chains/evm/client/errors.go
index f92a79e203..0bac56d142 100644
--- a/core/chains/evm/client/errors.go
+++ b/core/chains/evm/client/errors.go
@@ -284,6 +284,16 @@ var gnosis = ClientErrors{
 	TransactionAlreadyInMempool: regexp.MustCompile(`(: |^)(alreadyknown)`),
 }
 
+var sei = ClientErrors{
+	// https://github.com/sei-protocol/sei-tendermint/blob/e9a22c961e83579d8a68cd045c532980d82fb2a0/types/mempool.go#L12
+	TransactionAlreadyInMempool: regexp.MustCompile("tx already exists in cache"),
+	// https://github.com/sei-protocol/sei-cosmos/blob/a4eb451c957b1ca7ca9118406682f93fe83d1f61/types/errors/errors.go#L50
+	// https://github.com/sei-protocol/sei-cosmos/blob/a4eb451c957b1ca7ca9118406682f93fe83d1f61/types/errors/errors.go#L56
+	// https://github.com/sei-protocol/sei-cosmos/blob/a4eb451c957b1ca7ca9118406682f93fe83d1f61/client/broadcast.go#L27
+	// https://github.com/sei-protocol/sei-cosmos/blob/a4eb451c957b1ca7ca9118406682f93fe83d1f61/types/errors/errors.go#L32
+	Fatal: regexp.MustCompile(`(: |^)'*out of gas|insufficient fee|Tx too large. Max size is \d+, but got \d+|: insufficient funds`),
+}
+
 const TerminallyStuckMsg = "transaction terminally stuck"
 
 // Tx.Error messages that are set internally so they are not chain or client specific
@@ -291,7 +301,7 @@ var internal = ClientErrors{
 	TerminallyStuck: regexp.MustCompile(TerminallyStuckMsg),
 }
 
-var clients = []ClientErrors{parity, geth, arbitrum, metis, substrate, avalanche, nethermind, harmony, besu, erigon, klaytn, celo, zkSync, zkEvm, treasure, mantle, aStar, hedera, gnosis, internal}
+var clients = []ClientErrors{parity, geth, arbitrum, metis, substrate, avalanche, nethermind, harmony, besu, erigon, klaytn, celo, zkSync, zkEvm, treasure, mantle, aStar, hedera, gnosis, sei, internal}
 
 // ClientErrorRegexes returns a map of compiled regexes for each error type
 func ClientErrorRegexes(errsRegex config.ClientErrors) *ClientErrors {
diff --git a/core/chains/evm/client/errors_test.go b/core/chains/evm/client/errors_test.go
index c8483972c8..7fba0ae51f 100644
--- a/core/chains/evm/client/errors_test.go
+++ b/core/chains/evm/client/errors_test.go
@@ -144,6 +144,7 @@ func Test_Eth_Errors(t *testing.T) {
 			{"client error transaction already in mempool", true, "tomlConfig"},
 			{"alreadyknown", true, "Gnosis"},
 			{"failed to forward tx to sequencer, please try again. Error message: 'already known'", true, "Mantle"},
+			{"tx already exists in cache", true, "Sei"},
 		}
 		for _, test := range tests {
 			err = evmclient.NewSendErrorS(test.message)
@@ -420,6 +421,11 @@ func Test_Eth_Errors_Fatal(t *testing.T) {
 		{"client error fatal", true, "tomlConfig"},
 		{"[Request ID: d9711488-4c1e-4af2-bc1f-7969913d7b60] Error invoking RPC: transaction 0.0.4425573@1718213476.914320044 failed precheck with status INVALID_SIGNATURE", true, "hedera"},
 		{"invalid chain id for signer", true, "Treasure"},
+
+		{": out of gas", true, "Sei"},
+		{"Tx too large. Max size is 2048576, but got 2097431", true, "Sei"},
+		{": insufficient funds", true, "Sei"},
+		{"insufficient fee", true, "Sei"},
 	}
 
 	for _, test := range tests {
diff --git a/core/chains/evm/config/chaintype/chaintype.go b/core/chains/evm/config/chaintype/chaintype.go
index f6b84e4655..71bcafb01a 100644
--- a/core/chains/evm/config/chaintype/chaintype.go
+++ b/core/chains/evm/config/chaintype/chaintype.go
@@ -22,6 +22,7 @@ const (
 	ChainXLayer          ChainType = "xlayer"
 	ChainZkEvm           ChainType = "zkevm"
 	ChainZkSync          ChainType = "zksync"
+	ChainSei             ChainType = "sei"
 )
 
 // IsL2 returns true if this chain is a Layer 2 chain. Notably:
@@ -38,7 +39,7 @@ func (c ChainType) IsL2() bool {
 
 func (c ChainType) IsValid() bool {
 	switch c {
-	case "", ChainArbitrum, ChainAstar, ChainCelo, ChainGnosis, ChainHedera, ChainKroma, ChainMantle, ChainMetis, ChainOptimismBedrock, ChainScroll, ChainWeMix, ChainXLayer, ChainZkEvm, ChainZkSync:
+	case "", ChainArbitrum, ChainAstar, ChainCelo, ChainGnosis, ChainHedera, ChainKroma, ChainMantle, ChainMetis, ChainOptimismBedrock, ChainScroll, ChainWeMix, ChainXLayer, ChainZkEvm, ChainZkSync, ChainSei:
 		return true
 	}
 	return false
@@ -74,6 +75,8 @@ func FromSlug(slug string) ChainType {
 		return ChainZkEvm
 	case "zksync":
 		return ChainZkSync
+	case "sei":
+		return ChainSei
 	default:
 		return ChainType(slug)
 	}
@@ -140,4 +143,5 @@ var ErrInvalid = fmt.Errorf("must be one of %s or omitted", strings.Join([]strin
 	string(ChainXLayer),
 	string(ChainZkEvm),
 	string(ChainZkSync),
+	string(ChainSei),
 }, ", "))
diff --git a/core/services/chainlink/config_test.go b/core/services/chainlink/config_test.go
index 9caf37ccf2..296ba60bfe 100644
--- a/core/services/chainlink/config_test.go
+++ b/core/services/chainlink/config_test.go
@@ -1357,7 +1357,7 @@ func TestConfig_Validate(t *testing.T) {
 		- 1: 10 errors:
 			- ChainType: invalid value (Foo): must not be set with this chain id
 			- Nodes: missing: must have at least one node
-			- ChainType: invalid value (Foo): must be one of arbitrum, astar, celo, gnosis, hedera, kroma, mantle, metis, optimismBedrock, scroll, wemix, xlayer, zkevm, zksync or omitted
+			- ChainType: invalid value (Foo): must be one of arbitrum, astar, celo, gnosis, hedera, kroma, mantle, metis, optimismBedrock, scroll, wemix, xlayer, zkevm, zksync, sei or omitted
 			- HeadTracker.HistoryDepth: invalid value (30): must be greater than or equal to FinalizedBlockOffset
 			- GasEstimator.BumpThreshold: invalid value (0): cannot be 0 if auto-purge feature is enabled for Foo
 			- Transactions.AutoPurge.Threshold: missing: needs to be set if auto-purge feature is enabled for Foo
@@ -1370,7 +1370,7 @@ func TestConfig_Validate(t *testing.T) {
 		- 2: 5 errors:
 			- ChainType: invalid value (Arbitrum): only "optimismBedrock" can be used with this chain id
 			- Nodes: missing: must have at least one node
-			- ChainType: invalid value (Arbitrum): must be one of arbitrum, astar, celo, gnosis, hedera, kroma, mantle, metis, optimismBedrock, scroll, wemix, xlayer, zkevm, zksync or omitted
+			- ChainType: invalid value (Arbitrum): must be one of arbitrum, astar, celo, gnosis, hedera, kroma, mantle, metis, optimismBedrock, scroll, wemix, xlayer, zkevm, zksync, sei or omitted
 			- FinalityDepth: invalid value (0): must be greater than or equal to 1
 			- MinIncomingConfirmations: invalid value (0): must be greater than or equal to 1
 		- 3: 3 errors: