diff --git a/src/core.rs b/src/core.rs
index 70fbea46..f74f8082 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -11,15 +11,29 @@ use serde::{Deserialize, Serialize};
 use starknet_crypto::FieldElement;
 
 use crate::hash::{pedersen_hash_array, StarkFelt, StarkHash};
-use crate::serde_utils::{BytesAsHex, PrefixedBytesAsHex};
+use crate::serde_utils::{deserialize_ascii_string, BytesAsHex, PrefixedBytesAsHex};
 use crate::transaction::{Calldata, ContractAddressSalt};
 use crate::{impl_from_through_intermediate, StarknetApiError};
 
-/// A chain id.
+/// A chain id. Must contain only ASCII characters.
 #[derive(Clone, Debug, Display, Eq, PartialEq, Hash, Deserialize, Serialize, PartialOrd, Ord)]
-pub struct ChainId(pub String);
+pub struct ChainId(#[serde(deserialize_with = "deserialize_ascii_string")] String);
 
 impl ChainId {
+    /// Returns a new [`ChainId`].
+    pub fn new(chain_id: String) -> Result<Self, StarknetApiError> {
+        match chain_id.chars().all(|c| c.is_ascii()) {
+            true => Ok(Self(chain_id)),
+            false => Err(StarknetApiError::OutOfRange { string: chain_id }),
+        }
+    }
+
+    /// Returns the chain id as a string.
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Returns the chain id as a hex string.
     pub fn as_hex(&self) -> String {
         format!("0x{}", hex::encode(&self.0))
     }
diff --git a/src/serde_utils.rs b/src/serde_utils.rs
index 067fddeb..8d53d887 100644
--- a/src/serde_utils.rs
+++ b/src/serde_utils.rs
@@ -3,9 +3,10 @@
 #[path = "serde_utils_test.rs"]
 mod serde_utils_test;
 
-use serde::de::{Deserialize, Visitor};
+use serde::de::{Deserialize, Error as DeserializationError, Visitor};
 use serde::ser::{Serialize, SerializeTuple};
 use serde::Deserializer;
+use serde_json::Value;
 
 use crate::deprecated_contract_class::ContractClassAbiEntry;
 
@@ -144,3 +145,20 @@ where
         Err(_) => Ok(None),
     }
 }
+
+pub fn deserialize_ascii_string<'de, D: Deserializer<'de>>(
+    deserializer: D,
+) -> Result<String, D::Error> {
+    let chian_id: _ = match Value::deserialize(deserializer)? {
+        Value::String(string) => match string.chars().all(|c| c.is_ascii()) {
+            true => string,
+            false => {
+                return Err(DeserializationError::custom(format!(
+                    "Chain id ({string}) must contain only ASCII characters."
+                )));
+            }
+        },
+        _ => return Err(DeserializationError::custom("Cannot cast value into String.")),
+    };
+    Ok(chian_id)
+}
diff --git a/src/serde_utils_test.rs b/src/serde_utils_test.rs
index b3d6134b..3e239bc7 100644
--- a/src/serde_utils_test.rs
+++ b/src/serde_utils_test.rs
@@ -175,3 +175,17 @@ fn deserialize_optional_contract_class_abi_entry_vector_none() {
     let res: DummyContractClass = serde_json::from_str(json).unwrap();
     assert_eq!(res, DummyContractClass { abi: None });
 }
+
+#[test]
+fn chain_id_non_ascii() {
+    let chain_id_str = r#""חלודה""#;
+    let chain_id = serde_json::from_str::<crate::core::ChainId>(chain_id_str);
+    assert_matches!(chain_id, Err(serde_json::Error { .. }));
+}
+
+#[test]
+fn valid_chain_id() {
+    let chain_id_str = r#""chain_ID""#;
+    let chain_id = serde_json::from_str::<crate::core::ChainId>(chain_id_str).unwrap();
+    assert_eq!(chain_id_str, serde_json::to_string(&chain_id).unwrap())
+}