Anecdotes

Has been in a relationship with Mad Men (2007) lead actor Jon Hamm since 1997. They live together in Los Angeles. They split up in 2015.

Jennifer received the Golden Satellite Award for Best Actress in a Musical or Comedy for her role as "Jessica Stein" in Les aventures romantiques de Jessica Stein (2001).

Westfeldt is one of two sisters. Their mother is of German Jewish and Russian Jewish descent. Their father is of English, and some Swedish, Irish, French, and Scottish, descent. Through him, the Westfeldt sisters are descended from a Swedish nobleman (whose surname was originally "Wästfeldt") and are thus included in the Swedish peerage.

Starred in two pilot episodes for network TV series that did not get chosen to air the following season. One was written by Paul Reiser, the other was called "Dante" and she played the agent of a fictional pro football player.

Won a 2004 Theater World Award for the Broadway revival of "Wonderful Town" and was nominated for Broadway's 2004 Tony Award for Best Actress (Featured Role - Musical) for the same role.

Attended Guilford High School in Guilford, CT, where she starred in several school theatrical productions. She attended Yale University.