Dave married Pamela Casselburry in 1991. They have a son named Justis David Mustaine and a daughter Electra Nicole Mustaine. Dave recently confirmed to Eddie Trunk that after 2 trial separations, he and Pam had reconciled.
Mustaine helped promote his wife Pam's coffee business, Net Worth Coffee Brokers, by creating a Dave Mustaine line of coffee and associated items, with part of the proceeds going to Door of Faith charity. The bags featured his silhouette with a guitar and his signature. Among the items in the line were Dave Mustaine's Peruvian Blend coffee, Black Gold Blend coffee, Decaff coffee, Dave Mustaine's Perfect Tea Maker, a Barrel Mug, Travel Tumbler, and a Christmas T-shirt. Mustaine announced the line would be discontinued in August 2009, though his wife's business would continue.