diff --git a/crates/gateway/src/errors.rs b/crates/gateway/src/errors.rs
index 8752fa02..10759bef 100644
--- a/crates/gateway/src/errors.rs
+++ b/crates/gateway/src/errors.rs
@@ -24,6 +24,14 @@ pub enum TransactionValidatorError {
     },
     #[error("The resource bounds mapping is missing a resource {resource:?}.")]
     MissingResource { resource: Resource },
+    #[error(
+        "Calldata length exceeded maximum: length {calldata_length}
+        (allowed length: {max_calldata_length})."
+    )]
+    CalldataTooLong {
+        calldata_length: usize,
+        max_calldata_length: usize,
+    },
 }
 
 pub type TransactionValidatorResult<T> = Result<T, TransactionValidatorError>;
diff --git a/crates/gateway/src/starknet_api_test_utils.rs b/crates/gateway/src/starknet_api_test_utils.rs
index 6d1975ad..f2310eab 100644
--- a/crates/gateway/src/starknet_api_test_utils.rs
+++ b/crates/gateway/src/starknet_api_test_utils.rs
@@ -4,7 +4,7 @@ use starknet_api::external_transaction::{
     ExternalDeployAccountTransactionV3, ExternalInvokeTransaction, ExternalInvokeTransactionV3,
     ExternalTransaction,
 };
-use starknet_api::transaction::{ResourceBounds, ResourceBoundsMapping};
+use starknet_api::transaction::{Calldata, ResourceBounds, ResourceBoundsMapping};
 
 // Utils.
 pub fn create_external_declare_tx_for_testing(
@@ -29,6 +29,7 @@ pub fn create_external_declare_tx_for_testing(
 
 pub fn create_external_deploy_account_tx_for_testing(
     resource_bounds: ResourceBoundsMapping,
+    constructor_calldata: Calldata,
 ) -> ExternalTransaction {
     ExternalTransaction::DeployAccount(ExternalDeployAccountTransaction::V3(
         ExternalDeployAccountTransactionV3 {
@@ -36,7 +37,7 @@ pub fn create_external_deploy_account_tx_for_testing(
             tip: Default::default(),
             contract_address_salt: Default::default(),
             class_hash: Default::default(),
-            constructor_calldata: Default::default(),
+            constructor_calldata,
             nonce: Default::default(),
             signature: Default::default(),
             nonce_data_availability_mode: DataAvailabilityMode::L1,
@@ -48,6 +49,7 @@ pub fn create_external_deploy_account_tx_for_testing(
 
 pub fn create_external_invoke_tx_for_testing(
     resource_bounds: ResourceBoundsMapping,
+    calldata: Calldata,
 ) -> ExternalTransaction {
     ExternalTransaction::Invoke(ExternalInvokeTransaction::V3(ExternalInvokeTransactionV3 {
         resource_bounds,
@@ -55,7 +57,7 @@ pub fn create_external_invoke_tx_for_testing(
         signature: Default::default(),
         nonce: Default::default(),
         sender_address: Default::default(),
-        calldata: Default::default(),
+        calldata,
         nonce_data_availability_mode: DataAvailabilityMode::L1,
         fee_data_availability_mode: DataAvailabilityMode::L1,
         paymaster_data: Default::default(),
diff --git a/crates/gateway/src/stateless_transaction_validator.rs b/crates/gateway/src/stateless_transaction_validator.rs
index ab75f0b8..1b29add8 100644
--- a/crates/gateway/src/stateless_transaction_validator.rs
+++ b/crates/gateway/src/stateless_transaction_validator.rs
@@ -15,6 +15,8 @@ pub struct TransactionValidatorConfig {
     // If true, validates that the reousrce bounds are not zero.
     pub validate_non_zero_l1_gas_fee: bool,
     pub validate_non_zero_l2_gas_fee: bool,
+
+    pub max_calldata_length: usize,
 }
 
 pub struct TransactionValidator {
@@ -25,9 +27,9 @@ impl TransactionValidator {
     pub fn validate(&self, tx: &ExternalTransaction) -> TransactionValidatorResult<()> {
         // TODO(Arni, 1/5/2024): Add a mechanism that validate the sender address is not blocked.
         // TODO(Arni, 1/5/2024): Validate transaction version.
-        // TODO(Arni, 4/4/2024): Validate tx signature and calldata are not too long.
 
         self.validate_fee(tx)?;
+        self.validate_tx_size(tx)?;
 
         Ok(())
     }
@@ -72,4 +74,40 @@ impl TransactionValidator {
 
         Ok(())
     }
+
+    fn validate_tx_size(&self, tx: &ExternalTransaction) -> TransactionValidatorResult<()> {
+        self.validate_tx_calldata_size(tx)?;
+
+        // TODO(Arni, 4/4/2024): Validate tx signature is not too long.
+
+        Ok(())
+    }
+
+    fn validate_tx_calldata_size(
+        &self,
+        tx: &ExternalTransaction,
+    ) -> TransactionValidatorResult<()> {
+        let calldata = match tx {
+            ExternalTransaction::Declare(_) => {
+                // Declare transaction has no calldata.
+                return Ok(());
+            }
+            ExternalTransaction::DeployAccount(tx) => match tx {
+                ExternalDeployAccountTransaction::V3(tx) => &tx.constructor_calldata,
+            },
+            ExternalTransaction::Invoke(tx) => match tx {
+                ExternalInvokeTransaction::V3(tx) => &tx.calldata,
+            },
+        };
+
+        let calldata_length = calldata.0.len();
+        if calldata_length > self.config.max_calldata_length {
+            return Err(TransactionValidatorError::CalldataTooLong {
+                calldata_length,
+                max_calldata_length: self.config.max_calldata_length,
+            });
+        }
+
+        Ok(())
+    }
 }
diff --git a/crates/gateway/src/stateless_transaction_validator_test.rs b/crates/gateway/src/stateless_transaction_validator_test.rs
index bf379715..88acd084 100644
--- a/crates/gateway/src/stateless_transaction_validator_test.rs
+++ b/crates/gateway/src/stateless_transaction_validator_test.rs
@@ -1,7 +1,9 @@
 use rstest::rstest;
 
+use starknet_api::calldata;
 use starknet_api::external_transaction::ExternalTransaction;
-use starknet_api::transaction::{Resource, ResourceBounds, ResourceBoundsMapping};
+use starknet_api::hash::StarkFelt;
+use starknet_api::transaction::{Calldata, Resource, ResourceBounds, ResourceBoundsMapping};
 
 use crate::starknet_api_test_utils::{
     create_external_declare_tx_for_testing, create_external_deploy_account_tx_for_testing,
@@ -16,47 +18,73 @@ use crate::stateless_transaction_validator::{
 const VALIDATOR_CONFIG_FOR_TESTING: TransactionValidatorConfig = TransactionValidatorConfig {
     validate_non_zero_l1_gas_fee: true,
     validate_non_zero_l2_gas_fee: false,
+    max_calldata_length: 1,
 };
 
-const VALIDATOR_CONFIG_FOR_L2_GAS_TESTING: TransactionValidatorConfig =
-    TransactionValidatorConfig {
-        validate_non_zero_l1_gas_fee: false,
-        validate_non_zero_l2_gas_fee: true,
-    };
-
 #[rstest]
 #[case::ignore_resource_bounds(
     TransactionValidatorConfig{
         validate_non_zero_l1_gas_fee: false,
         validate_non_zero_l2_gas_fee: false,
+        ..VALIDATOR_CONFIG_FOR_TESTING
     },
-    create_external_invoke_tx_for_testing(zero_resource_bounds_mapping()),
+    create_external_invoke_tx_for_testing(zero_resource_bounds_mapping(), calldata![]),
     Ok(())
 )]
 #[case::missing_l1_gas_resource_bounds(
-    VALIDATOR_CONFIG_FOR_TESTING,
-    create_external_invoke_tx_for_testing(ResourceBoundsMapping::default()),
+    TransactionValidatorConfig{
+        validate_non_zero_l1_gas_fee: true,
+        ..VALIDATOR_CONFIG_FOR_TESTING
+    },
+    create_external_invoke_tx_for_testing(ResourceBoundsMapping::default(), calldata![]),
     Err(TransactionValidatorError::MissingResource { resource: Resource::L1Gas })
 )]
 #[case::missing_l2_gas_resource_bounds(
-    VALIDATOR_CONFIG_FOR_L2_GAS_TESTING,
-    create_external_invoke_tx_for_testing(ResourceBoundsMapping::default()),
+    TransactionValidatorConfig{
+        validate_non_zero_l1_gas_fee: false,
+        validate_non_zero_l2_gas_fee: true,
+        ..VALIDATOR_CONFIG_FOR_TESTING
+    },
+    create_external_invoke_tx_for_testing(ResourceBoundsMapping::default(), calldata![]),
     Err(TransactionValidatorError::MissingResource { resource: Resource::L2Gas })
 )]
 #[case::zero_l1_gas_resource_bounds(
-    VALIDATOR_CONFIG_FOR_TESTING,
-    create_external_invoke_tx_for_testing(zero_resource_bounds_mapping()),
+    TransactionValidatorConfig{
+        validate_non_zero_l1_gas_fee: true,
+        ..VALIDATOR_CONFIG_FOR_TESTING
+    },
+    create_external_invoke_tx_for_testing(zero_resource_bounds_mapping(), calldata![]),
     Err(TransactionValidatorError::ZeroFee{
         resource: Resource::L1Gas, resource_bounds: ResourceBounds::default()
     })
 )]
 #[case::zero_l2_gas_resource_bounds(
-    VALIDATOR_CONFIG_FOR_L2_GAS_TESTING,
-    create_external_invoke_tx_for_testing(non_zero_l1_resource_bounds_mapping()),
+    TransactionValidatorConfig{
+        validate_non_zero_l1_gas_fee: false,
+        validate_non_zero_l2_gas_fee: true,
+        ..VALIDATOR_CONFIG_FOR_TESTING
+    },
+    create_external_invoke_tx_for_testing(non_zero_l1_resource_bounds_mapping(), calldata![]),
     Err(TransactionValidatorError::ZeroFee{
         resource: Resource::L2Gas, resource_bounds: ResourceBounds::default()
     })
 )]
+#[case::deploy_account_calldata_too_long(
+    VALIDATOR_CONFIG_FOR_TESTING,
+    create_external_deploy_account_tx_for_testing(
+        non_zero_l1_resource_bounds_mapping(),
+        calldata![StarkFelt::from_u128(1),StarkFelt::from_u128(2)],
+    ),
+    Err(TransactionValidatorError::CalldataTooLong { calldata_length: 2, max_calldata_length: 1 })
+)]
+#[case::invoke_calldata_too_long(
+    VALIDATOR_CONFIG_FOR_TESTING,
+    create_external_invoke_tx_for_testing(
+        non_zero_l1_resource_bounds_mapping(),
+        calldata![StarkFelt::from_u128(1),StarkFelt::from_u128(2)],
+    ),
+    Err(TransactionValidatorError::CalldataTooLong { calldata_length: 2, max_calldata_length: 1 })
+)]
 #[case::valid_declare_tx(
     VALIDATOR_CONFIG_FOR_TESTING,
     create_external_declare_tx_for_testing(non_zero_l1_resource_bounds_mapping()),
@@ -64,17 +92,21 @@ const VALIDATOR_CONFIG_FOR_L2_GAS_TESTING: TransactionValidatorConfig =
 )]
 #[case::valid_deploy_account_tx(
     VALIDATOR_CONFIG_FOR_TESTING,
-    create_external_deploy_account_tx_for_testing(non_zero_l1_resource_bounds_mapping(),),
+    create_external_deploy_account_tx_for_testing(non_zero_l1_resource_bounds_mapping(), calldata![]),
     Ok(())
 )]
 #[case::valid_invoke_tx(
     VALIDATOR_CONFIG_FOR_TESTING,
-    create_external_invoke_tx_for_testing(non_zero_l1_resource_bounds_mapping()),
+    create_external_invoke_tx_for_testing(non_zero_l1_resource_bounds_mapping(), calldata![]),
     Ok(())
 )]
 #[case::valid_l2_gas_invoke_tx(
-    VALIDATOR_CONFIG_FOR_L2_GAS_TESTING,
-    create_external_invoke_tx_for_testing(non_zero_l2_resource_bounds_mapping()),
+    TransactionValidatorConfig{
+        validate_non_zero_l1_gas_fee: false,
+        validate_non_zero_l2_gas_fee: true,
+        ..VALIDATOR_CONFIG_FOR_TESTING
+    },
+    create_external_invoke_tx_for_testing(non_zero_l2_resource_bounds_mapping(), calldata![]),
     Ok(())
 )]
 fn test_transaction_validator(