Kutcher dated actresses January Jones (from 1998 to 2001), Ashley Scott (from 2001 to 2002), Monet Mazur (2002), and Brittany Murphy (from 2002 to 2003). Following his break-up with Murphy in early 2003, Kutcher began dating Demi Moore; reports in the media frequently commented on the fifteen-year age difference between the two. Moore and Kutcher married on September 24, 2005 in a private ceremony conducted by a rabbi of the Kabbalah Centre; the wedding was attended by about 100 close friends and family of the couple, including Bruce Willis, Moore's ex-husband.

Both Kutcher and Moore are followers of the Kabbalah Centre, a controversial California-based organization which alleges that it teaches Kabbalah, a form of Jewish mysticism. As part of his involvement in Kabbalah, Kutcher has toured Israel with Demi Moore, as well as taken time off to observe traditional Jewish High Holy Days, and celebrated the Jewish holiday Purim. Kutcher also usually wears the traditional Kabbalah