Jennifer earned a theater degree from Ohio’s Denison University. After college, she moved to New York and began auditioning for stage roles, landing her first part only a month after arriving in town as an understudy in the Broadway production of A Month in the Country. She earned $150 a week for the role and moon-lighted as a hostess at Isabella’s restaurant.

Jennifer had to go through five rounds of auditions before she was given the role of Felicity in 1998. Jennifer met her ex-husband Scott Foley on the set of the show. The couple divorced in 2003. She is now married to Ben Affleck, and the couple's daughter Violet was born in December 2005. In August 2008, Jennifer revealed she was pregnant with their second child.

She has appeared in numerous other television production as well as such films as Elektra (2005), 13 Going on 30 (2004), Daredevil (2003), Pearl Harbor (2001) and Dude, Where's My Car? (2000). Aside from filming "Alias" (2001), Jennifer enjoys cooking, gardening, hiking, and inspired by her character on the show, kickboxing.

In addition to her daily workouts, Jennifer is a strict believer in a nutrition plan that recommends eating every three hours. The meals, which Jennifer usually makes herself, include small servings of proteins and high-quality carbs.

On getting her ears pierced for the 2006 Oscars: "A couple of months before the ceremony, I went to pick out the jewelry I’d be wearing on the night. I picked out the diamond cuff and the hair clip, and then they showed me the most gorgeous pair of earrings I’d ever seen. It wasn’t until I came to try them on that I realized they’d forgotten I didn’t have pierced ears. They could see how much I loved them, and how disappointed I was that I couldn’t wear them, so they said that, if I really wanted to, they could pierce my ears for me there and then. That would give them enough time to heal before the ceremony, and I could then wear the earrings. And I really did want to wear those earrings, so I said ‘OK’ and they pierced my ears for me before I left the boutique. It felt a bit odd to have them done, although I did have them pierced for a couple of weeks a few years back for a movie I was in ("Aftershock: Earthquake in New York"), but it was worth it because I knew it meant I’d be wearing those fabulous earrings to the ceremony."