Off the screen, Kate has dated Michael Sheen for a number of years. The two have a daughter together. In June 2003, she became engaged to the director of Underworld, Len Wiseman, and the two were wed in May 2004 in Bel-Air, California.

The couple immediately continued their working relationship with a sequel to Underworld.

In 2005, she will return as Selene in the sequel, Underworld: Evolution, and in 2006, she can be seen in Click with Adam Sandler.