diff --git a/transaction.go b/transaction.go
index e09699e7..8d45c676 100644
--- a/transaction.go
+++ b/transaction.go
@@ -163,8 +163,9 @@ type TransactionOption interface {
 }
 
 type transactionOptions struct {
-	payer         PublicKey
-	addressTables map[PublicKey]PublicKeySlice // [tablePubkey]addresses
+	payer                 PublicKey
+	addressTables         map[PublicKey]PublicKeySlice // [tablePubkey]addresses
+	deterministicOrdering bool                         // sort lookup tables for deterministic serialization
 }
 
 type transactionOptionFunc func(opts *transactionOptions)
@@ -181,6 +182,14 @@ func TransactionAddressTables(tables map[PublicKey]PublicKeySlice) TransactionOp
 	return transactionOptionFunc(func(opts *transactionOptions) { opts.addressTables = tables })
 }
 
+// TransactionDeterministicOrdering ensures deterministic transaction serialization
+// when using multiple address lookup tables. Without this option, map iteration
+// order may cause account indices to vary between runs. Enable this for testing,
+// caching, or any scenario requiring consistent transaction bytes.
+func TransactionDeterministicOrdering() TransactionOption {
+	return transactionOptionFunc(func(opts *transactionOptions) { opts.deterministicOrdering = true })
+}
+
 var debugNewTransaction = false
 
 type TransactionBuilder struct {
@@ -233,6 +242,21 @@ type addressTablePubkeyWithIndex struct {
 	index        uint8
 }
 
+// sortedMapKeys returns the keys of a map, optionally sorted by byte comparison.
+// When sortKeys is false, returns keys in arbitrary map iteration order.
+func sortedMapKeys[V any](m map[PublicKey]V, sortKeys bool) []PublicKey {
+	keys := make([]PublicKey, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	if sortKeys {
+		sort.SliceStable(keys, func(i, j int) bool {
+			return bytes.Compare(keys[i][:], keys[j][:]) < 0
+		})
+	}
+	return keys
+}
+
 func NewTransaction(instructions []Instruction, recentBlockHash Hash, opts ...TransactionOption) (*Transaction, error) {
 	if len(instructions) == 0 {
 		return nil, fmt.Errorf("requires at-least one instruction to create a transaction")
@@ -259,7 +283,11 @@ func NewTransaction(instructions []Instruction, recentBlockHash Hash, opts ...Tr
 	}
 
 	addressLookupKeysMap := make(map[PublicKey]addressTablePubkeyWithIndex) // all accounts from tables as map
-	for addressTablePubKey, addressTable := range options.addressTables {
+
+	// When deterministicOrdering is enabled, sort keys for consistent behavior
+	// when addresses appear in multiple tables (first table in sorted order wins).
+	for _, addressTablePubKey := range sortedMapKeys(options.addressTables, options.deterministicOrdering) {
+		addressTable := options.addressTables[addressTablePubKey]
 		if len(addressTable) > 256 {
 			return nil, fmt.Errorf("max lookup table index exceeded for %s table", addressTablePubKey)
 		}
@@ -412,7 +440,10 @@ func NewTransaction(instructions []Instruction, recentBlockHash Hash, opts ...Tr
 	if len(lookupsMap) > 0 {
 		lookups := make([]MessageAddressTableLookup, 0, len(lookupsMap))
 
-		for tablePubKey, l := range lookupsMap {
+		// When deterministicOrdering is enabled, sort keys for consistent
+		// transaction serialization across runs.
+		for _, tablePubKey := range sortedMapKeys(lookupsMap, options.deterministicOrdering) {
+			l := lookupsMap[tablePubKey]
 			lookupsWritableKeys = append(lookupsWritableKeys, l.Writable...)
 			lookupsReadOnlyKeys = append(lookupsReadOnlyKeys, l.Readonly...)
 
diff --git a/transaction_test.go b/transaction_test.go
index e1c19fe1..b4a48b37 100644
--- a/transaction_test.go
+++ b/transaction_test.go
@@ -399,3 +399,74 @@ func BenchmarkTransactionVerifySignatures(b *testing.B) {
 		tx.VerifySignatures()
 	}
 }
+
+// TestNewTransactionWithAddressLookupTables_Deterministic verifies that transaction
+// serialization is deterministic when using TransactionDeterministicOrdering with
+// multiple address lookup tables.
+func TestNewTransactionWithAddressLookupTables_Deterministic(t *testing.T) {
+	// Define two lookup tables
+	lookupTable1 := MustPublicKeyFromBase58("8Vaso6eE1pWktDHwy2qQBB1fhjmBgwzhoXQKe1sxtFjn")
+	lookupTable2 := MustPublicKeyFromBase58("FqtwFavD9v99FvoaZrY14bGatCQa9ChsMVphEUNAWHeG")
+
+	// Addresses unique to lookup table 1
+	addr1InTable1 := MustPublicKeyFromBase58("TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA")
+	addr2InTable1 := MustPublicKeyFromBase58("JUP6LkbZbjS1jKKwapdHNy74zcZ3tLUZoi5QNyVTaV4")
+
+	// Addresses unique to lookup table 2
+	addr1InTable2 := MustPublicKeyFromBase58("TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb")
+	addr2InTable2 := MustPublicKeyFromBase58("ATokenGPvbdGVxr1b2hvZbsiqW5xWH25efTNsLJA8knL")
+
+	// Shared address that exists in BOTH tables - tests that deterministic
+	// ordering consistently picks the same table when an address appears in multiple
+	sharedAddr := MustPublicKeyFromBase58("So11111111111111111111111111111111111111112")
+
+	// Fee payer and program
+	feePayer := MustPublicKeyFromBase58("7KxrPswMgoVFwC1K7KmudEW9KzmVUCdBnLBMaSAjYQGp")
+	programID := MustPublicKeyFromBase58("11111111111111111111111111111111")
+
+	addressTables := map[PublicKey]PublicKeySlice{
+		lookupTable1: {addr1InTable1, addr2InTable1, sharedAddr},
+		lookupTable2: {sharedAddr, addr1InTable2, addr2InTable2}, // sharedAddr at different index
+	}
+
+	// Create instruction that uses accounts from both lookup tables, including the shared address
+	instruction := &testTransactionInstructions{
+		accounts: []*AccountMeta{
+			{PublicKey: feePayer, IsSigner: true, IsWritable: true},
+			{PublicKey: addr1InTable1, IsSigner: false, IsWritable: false},
+			{PublicKey: addr2InTable1, IsSigner: false, IsWritable: true},
+			{PublicKey: sharedAddr, IsSigner: false, IsWritable: true}, // shared address
+			{PublicKey: addr1InTable2, IsSigner: false, IsWritable: false},
+			{PublicKey: addr2InTable2, IsSigner: false, IsWritable: true},
+		},
+		data:      []byte{0x01, 0x02, 0x03},
+		programID: programID,
+	}
+
+	blockhash := MustHashFromBase58("4sGjMW1sUnHzSxGspuhpqLDx6wiyjNtZAMdL4VZHirAn")
+
+	// Build the transaction multiple times WITH deterministic ordering
+	// and verify consistent serialization
+	var firstSerialized []byte
+	for i := 0; i < 100; i++ {
+		tx, err := NewTransaction(
+			[]Instruction{instruction},
+			blockhash,
+			TransactionPayer(feePayer),
+			TransactionAddressTables(addressTables),
+			TransactionDeterministicOrdering(), // Enable deterministic ordering
+		)
+		require.NoError(t, err)
+
+		serialized, err := tx.MarshalBinary()
+		require.NoError(t, err)
+
+		if i == 0 {
+			firstSerialized = serialized
+		} else {
+			// Every iteration should produce identical bytes
+			assert.Equal(t, firstSerialized, serialized,
+				"Transaction serialization should be deterministic (iteration %d)", i)
+		}
+	}
+}