We know that Jesus spoke Aramaic because the gospel writers quote some of the Aramaic phrases he used and translate them for their Greek readers (e.g. Mk 5:41). It has also been suggested by some that Jesus spoke Greek but there is no consensus concerning his fluency. In Mark for Everyone by Tom Wright which I recently reviewed Wright makes the startling statement: “It is virtually certain that, though Jesus and his followers would be able to speak and understand Greek, their normal everyday language would be Aramaic” (63). I say this is surprising because no one had previously suggested to me that some Galilean fishermen would be able to speak Greek. I could conceive of a tax collector speaking Greek but a fisherman? I had always been led to believe they were uneducated country bumpkins.
Although Google will provide a lot of results for the question “Did Jesus Speak Greek” there does not seem to be a lot of scholarly work done on the subject. Michael Wise in the Dictionary of Jesus and the Gospels from IVP is not nearly as emphatic as Wright, stating “The question whether [Jesus] also knew Hebrew and Greek can only be answered on theoretical grounds” (442). I have come across two articles by Stanley Porter that assert Jesus could not only speak Greek but has fluent enough to teach in that language. Obviously this has implications for interpreting the gospel accounts of his public ministry. They would not just be second hand translations of his teaching but could be the actual words he spoke.
Stanley E. Porter, “Did Jesus Ever Teach in Greek?” Tyndale Bulletin. 44:2 (1993): 199-235.
“…it is virtually certain that he used Greek at various times in his itinerant ministry” (235).
Stanley E. Porter, “Jesus and the Use of Greek: A Response to Maurice Casey.” Bulletin for Biblical Research. 10:1 (2000): 71-87.
As may be deduced from the title of the above article not everyone agrees with Porter’s conclusion, namely:
P. Maurice Casey, “In Which Language Did Jesus Teach?” Expository Times. 108:11 (1997) 326-28.
Casey argues for the use of Aramaic by Jesus in his teaching. No one is willing to argue that Jesus would not have known some Greek but the question is whether he was fluent enough to teach in that language. The consensus seems to be that it is likely that he spoke to some people in Greek because it is less likely that they knew Aramaic than that he would not have known Greek. In other words it is an argument based on probabilities and silence. Aren’t those the best kind? 
