diff --git a/chronik/chronik-indexer/src/query/util.rs b/chronik/chronik-indexer/src/query/util.rs
--- a/chronik/chronik-indexer/src/query/util.rs
+++ b/chronik/chronik-indexer/src/query/util.rs
@@ -5,7 +5,10 @@
 use std::collections::{hash_map::Entry, BTreeMap, HashMap};
 
 use abc_rust_error::Result;
-use bitcoinsuite_core::tx::{OutPoint, SpentBy, Tx, TxId};
+use bitcoinsuite_core::{
+    ser::BitcoinSer,
+    tx::{OutPoint, SpentBy, Tx, TxId},
+};
 use chronik_db::io::{DbBlock, SpentByEntry, SpentByReader, TxNum, TxReader};
 use chronik_proto::proto;
 use thiserror::Error;
@@ -81,6 +84,7 @@
             is_final: avalanche.is_final_height(block.height),
         }),
         time_first_seen,
+        size: tx.ser_len() as u32,
         is_coinbase,
     }
 }
diff --git a/chronik/chronik-proto/proto/chronik.proto b/chronik/chronik-proto/proto/chronik.proto
--- a/chronik/chronik-proto/proto/chronik.proto
+++ b/chronik/chronik-proto/proto/chronik.proto
@@ -74,6 +74,8 @@
     BlockMetadata block = 8;
     // Time this tx has first been added to the mempool, or 0 if unknown
     int64 time_first_seen = 9;
+    // Serialized size of the tx
+    uint32 size = 11;
     // Whether this tx is a coinbase tx
     bool is_coinbase = 12;
 }
diff --git a/test/functional/chronik_script_unconfirmed_txs.py b/test/functional/chronik_script_unconfirmed_txs.py
--- a/test/functional/chronik_script_unconfirmed_txs.py
+++ b/test/functional/chronik_script_unconfirmed_txs.py
@@ -142,6 +142,7 @@
                     ),
                 ],
                 lock_time=1,
+                size=len(tx.serialize()),
                 time_first_seen=time_first_seen,
             ))
 
diff --git a/test/functional/chronik_tx.py b/test/functional/chronik_tx.py
--- a/test/functional/chronik_tx.py
+++ b/test/functional/chronik_tx.py
@@ -94,6 +94,7 @@
             lock_time=1234567890,
             block=None,
             time_first_seen=1333333337,
+            size=len(tx.serialize()),
             is_coinbase=False,
         )
 
@@ -143,6 +144,7 @@
             lock_time=12,
             block=None,
             time_first_seen=1333333338,
+            size=len(tx2.serialize()),
             is_coinbase=False,
         )
 
diff --git a/test/functional/test_framework/chronik/test_data.py b/test/functional/test_framework/chronik/test_data.py
--- a/test/functional/test_framework/chronik/test_data.py
+++ b/test/functional/test_framework/chronik/test_data.py
@@ -33,5 +33,6 @@
             timestamp=TIME_GENESIS_BLOCK,
         ),
         time_first_seen=0,
+        size=204,
         is_coinbase=True,
     )