Cicero’s friend and correspondent Titus Pomponius Atticus was a key figure in the Graeco-Roman cultural life of his time, and knowing about the Greek that he used would give us insight not only into this broader culture, but also into the Greek language itself at this crucial point of its history. However, no writings by him survive, and his Greek can only be reconstructed from Cicero’s letters. The only previous attempt to do this was made nearly a century ago and was generously inclusive but lacking in discernment. The current study seeks to distinguish the different types of evidence on this question that Cicero’s letters can offer. It provides a list of those Greek words we can be most confident featured in Atticus’ letters and suggests some criteria for judging the more numerous doubtful instances. Finally, it points to some conclusions about Atticus’ Greek, and how this may have differed from Cicero’s.