Aristarchus was a missionary companion of Paul from Thessalonica (Acts 20:4). He was with Paul in Ephesus, Jerusalem, and during his voyage to Rome (Acts 19:29; Acts 20:4; Acts 27:2). Most likely he is mentioned because he was known to Philemon and the church in Colossae.
24 and so do Mark, Aristarchus, Demas, and Luke, my fellow workers.