diff --git a/crates/config/src/lib.rs b/crates/config/src/lib.rs
index a7da5dc1f9d45..d48bfd66f59e2 100644
--- a/crates/config/src/lib.rs
+++ b/crates/config/src/lib.rs
@@ -346,7 +346,10 @@ pub struct Config {
     /// the initial balance of each deployed test contract
     pub initial_balance: U256,
     /// the block.number value during EVM execution
-    #[serde(deserialize_with = "crate::deser_u64_to_u256")]
+    #[serde(
+        deserialize_with = "crate::deserialize_u64_to_u256",
+        serialize_with = "crate::serialize_u64_or_u256"
+    )]
     pub block_number: U256,
     /// pins the block number for the state fork
     pub fork_block_number: Option<u64>,
@@ -367,7 +370,10 @@ pub struct Config {
     /// The `block.coinbase` value during EVM execution.
     pub block_coinbase: Address,
     /// The `block.timestamp` value during EVM execution.
-    #[serde(deserialize_with = "crate::deser_u64_to_u256")]
+    #[serde(
+        deserialize_with = "crate::deserialize_u64_to_u256",
+        serialize_with = "crate::serialize_u64_or_u256"
+    )]
     pub block_timestamp: U256,
     /// The `block.difficulty` value during EVM execution.
     pub block_difficulty: u64,
@@ -3737,8 +3743,8 @@ mod tests {
                 block_coinbase = '0x0000000000000000000000000000000000000000'
                 block_difficulty = 0
                 block_prevrandao = '0x0000000000000000000000000000000000000000000000000000000000000000'
-                block_number = "0x1"
-                block_timestamp = "0x1"
+                block_number = 1
+                block_timestamp = 1
                 use_literal_content = false
                 bytecode_hash = 'ipfs'
                 cbor_metadata = true
diff --git a/crates/config/src/utils.rs b/crates/config/src/utils.rs
index 6eeb3e3f67f93..8b316c0da9ca0 100644
--- a/crates/config/src/utils.rs
+++ b/crates/config/src/utils.rs
@@ -8,7 +8,7 @@ use foundry_compilers::artifacts::{
     remappings::{Remapping, RemappingError},
 };
 use revm::primitives::hardfork::SpecId;
-use serde::{Deserialize, Deserializer, de::Error};
+use serde::{Deserialize, Deserializer, Serializer, de::Error};
 use std::{
     io,
     path::{Path, PathBuf},
@@ -214,7 +214,7 @@ where
 }
 
 /// Deserialize into `U256` from either a `u64` or a `U256` hex string.
-pub fn deser_u64_to_u256<'de, D>(deserializer: D) -> Result<U256, D::Error>
+pub fn deserialize_u64_to_u256<'de, D>(deserializer: D) -> Result<U256, D::Error>
 where
     D: Deserializer<'de>,
 {
@@ -231,6 +231,26 @@ where
     }
 }
 
+/// Serialize `U256` as `u64` if it fits, otherwise as a hex string.
+/// If the number fits into a i64, serialize it as number without quotation marks.
+/// If the number fits into a u64, serialize it as a stringified number with quotation marks.
+/// Otherwise, serialize it as a hex string with quotation marks.
+pub fn serialize_u64_or_u256<S>(n: &U256, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    // The TOML specification handles integers as i64 so the number representation is limited to
+    // i64. If the number is larger than `i64::MAX` and up to `u64::MAX`, we serialize it as a
+    // string to avoid losing precision.
+    if let Ok(n_i64) = i64::try_from(*n) {
+        serializer.serialize_i64(n_i64)
+    } else if let Ok(n_u64) = u64::try_from(*n) {
+        serializer.serialize_str(&n_u64.to_string())
+    } else {
+        serializer.serialize_str(&format!("{n:#x}"))
+    }
+}
+
 /// Helper type to parse both `u64` and `U256`
 #[derive(Clone, Copy, Deserialize)]
 #[serde(untagged)]
diff --git a/crates/evm/core/src/opts.rs b/crates/evm/core/src/opts.rs
index d86a694cb4560..5cf7321647acb 100644
--- a/crates/evm/core/src/opts.rs
+++ b/crates/evm/core/src/opts.rs
@@ -278,11 +278,17 @@ pub struct Env {
     pub block_coinbase: Address,
 
     /// the block.timestamp value during EVM execution
-    #[serde(deserialize_with = "foundry_config::deser_u64_to_u256")]
+    #[serde(
+        deserialize_with = "foundry_config::deserialize_u64_to_u256",
+        serialize_with = "foundry_config::serialize_u64_or_u256"
+    )]
     pub block_timestamp: U256,
 
     /// the block.number value during EVM execution"
-    #[serde(deserialize_with = "foundry_config::deser_u64_to_u256")]
+    #[serde(
+        deserialize_with = "foundry_config::deserialize_u64_to_u256",
+        serialize_with = "foundry_config::serialize_u64_or_u256"
+    )]
     pub block_number: U256,
 
     /// the block.difficulty value during EVM execution
diff --git a/crates/forge/tests/cli/config.rs b/crates/forge/tests/cli/config.rs
index f2f737914fa0e..bcfaca725678e 100644
--- a/crates/forge/tests/cli/config.rs
+++ b/crates/forge/tests/cli/config.rs
@@ -1016,11 +1016,11 @@ prompt_timeout = 120
 sender = "0x1804c8ab1f12e6bbf3894d4083f33e07309d1f38"
 tx_origin = "0x1804c8ab1f12e6bbf3894d4083f33e07309d1f38"
 initial_balance = "0xffffffffffffffffffffffff"
-block_number = "0x1"
+block_number = 1
 gas_limit = 1073741824
 block_base_fee_per_gas = 0
 block_coinbase = "0x0000000000000000000000000000000000000000"
-block_timestamp = "0x1"
+block_timestamp = 1
 block_difficulty = 0
 block_prevrandao = "0x0000000000000000000000000000000000000000000000000000000000000000"
 memory_limit = 134217728
@@ -1242,7 +1242,7 @@ exclude = []
   "sender": "0x1804c8ab1f12e6bbf3894d4083f33e07309d1f38",
   "tx_origin": "0x1804c8ab1f12e6bbf3894d4083f33e07309d1f38",
   "initial_balance": "0xffffffffffffffffffffffff",
-  "block_number": "0x1",
+  "block_number": 1,
   "fork_block_number": null,
   "chain_id": null,
   "gas_limit": 1073741824,
@@ -1250,7 +1250,7 @@ exclude = []
   "gas_price": null,
   "block_base_fee_per_gas": 0,
   "block_coinbase": "0x0000000000000000000000000000000000000000",
-  "block_timestamp": "0x1",
+  "block_timestamp": 1,
   "block_difficulty": 0,
   "block_prevrandao": "0x0000000000000000000000000000000000000000000000000000000000000000",
   "block_gas_limit": null,