Mark Alt was born on October 18, 1991 in Kansas City, Missouri. A product of Cretin-Derham Hall High School in Minnesota where he also starred on the football field, Alt was selected in the second round of the 2010 NHL Entry Draft by the Carolina Hurricanes. He would then attend the University of Minnesota, suiting up for three seasons for the Golden Gophers.
On January 13, 2013, Alt's NHL rights were traded to the Philadelphia Flyers. He would make his professional debut in the late stages of the 2012-13 season for the Adirondack Phantoms of the American Hockey League.
Alt would spend the majority of the next four seasons with the Phantoms, seeing NHL action in just a single game on March 28, 2015. A 3-2 loss to the San Jose Sharks.