Since 1999, Barrett has been married to fellow Notre Dame Law School graduate Jesse M. Barrett, a partner at SouthBank Legal in South Bend, Indiana. Previously, Jesse Barrett worked as an Assistant U.S. Attorney for the Northern District of Indiana for 13 years. They live in South Bend and have seven children, ranging in age over a decade, two of whom were adopted from Haiti. Her adopted son became part of the family after the 2010 Haiti earthquake. Their youngest biological child has Down syndrome.

Barrett is a practicing Catholic and also has been an active participant with the small, tightly-knit, nondenominational Charismatic Christian intentional community People of Praise. Founded in South Bend, the self-described ecumenical "covenant community" is associated with the Catholic charismatic renewal movement although it is not formally affiliated with the Catholic Church. Approximately 90% of its members are Catholic.In 2015, Barrett signed a letter to the Synod on the Family, giving witness that the Church's teachings on marriage and family are "founded on the indissoluble commitment of a man and a woman".