Robertson was the second member of Barenaked Ladies to get married, and the first to have children. He married his longtime girlfriend, Natalie Herbert, in June 1994. They had their first child, Hannah on November 17, 1995; their second child, Lyle was born September 29, 1999; and their third child, Arden was born August 7, 2002. As the first in the band to have children, he was also one of the first to advocate for spending less time touring and more time at home with family. When he is not working with Barenaked Ladies, Robertson prefers to spend as much time as he can with his family in Toronto, or at their Bancroft-area cottage.