There have been numerous suggestions regarding Luke’s source for his list of nations in the Acts 2 Pentecost event. Scholars have looked to Persian inscriptions, geographical astrology, Roman imperial boasts, and the writings of Philo and Josephus as possible sources for Luke’s list. In this paper, I will argue that while these other lists demonstrate the commonality of the structure and purposes of ‘lists of nations’ throughout history, none of them provide a likely source for Acts 2. Rather, I propose that Luke has used a source from the Jerusalem church to ascertain the ethnicities of those present in the earliest times of the post-Pentecost Jesus movement.