The Suburgatory star and his wife Addie Lane, who announced in December that they were expecting a baby, welcomed their first son on March 9.
Sisto, who announced the birth on his Twitter page, again used the social networking site to reveal his son's name.
"Little man finally told us his name," he wrote. "BASTIAN KICK SISTO."
Sisto and Lane married in a small ceremony in New York in 2009.
The couple already have a 2-year-old daughter, Charlie Ballerina.