Hallisay was born in Washington, D.C., graduated from Gonzaga College High School in 1996 and then moved on to Cornell University, graduating in 2000. After college and before moving to Los Angeles, he worked on Wall Street. He says, "I was slaving away at that and I had a really good time with it, but it got to the point where I said, "You know, I had always dreamed about seeing what acting was all about."