03/09/2012 03:09 pm ET Updated Mar 09, 2012

Jon Hamm Dating Jennifer Westfeldt: 'Mad Men' Actor Reveals Why He Won't Marry

Jon Hamm may play a womanizer on "Mad Men," but in real life, the actor is nothing like philandering ad executive Don Draper -- especially when it comes to relationships.

In the April issue of ELLE UK, on newsstands Friday, Hamm opens up about why he isn't married to longtime girlfriend Jennifer Westfeldt.

"The flip answer is, if it ain't broke don't fix it," the actor said of their 15-year relationship. "The better version of that is, that any relationship is a day-in-day-out process."

Hamm adds that the couple is dedicated to one another, even if they aren't married. "Having a piece of paper serves to remind you of your commitment, but we do a pretty good job of reminding each other," he told the magazine.

In July 2010, he told Parade: "Jen is the love of my life, and we've already been together four times longer than my parents were married."

He added: "I don't have the marriage chip, and neither of us have the greatest examples of marriages in our families."

The pair first met at a party in 1997. Hamm and Westfeldt star in "Friends With Kids," written and directed by Westfeldt, which hits theaters Friday.