Mitchell was a four-year member of the South Mecklenburg High School swim team, serving as the team captain from 2012-13. He was named to the All-Region Second Team and All-Conference First Team and was a three-time team Most Valuable Performer. He helped his team to a third-place finish at the 2013 state championships and a conference championship in 2013. His father, Jim, was a track and field and cross country runner at the University of North Carolina, competing at three Olympic Trials.
Mitchel again competed at the Miami Invite where he won the 100 back and placed 3rd in the 200 free. At UAAs, Mitchell won the 100 back in a best time and placed 3rd in both the 200 free and 500 free. At NCAAs, Mitchell dropped more time in the 100 back(49.89) and also swam the 400 IM and 500 free.
Mitchell swam at the Miami Invite and dropped in his events. He placed 3rd in the mile and 5th in the 400 IM. At UAAs, Mitchell dropped even more time and placed 2nd in the 400 IM(3:59.54) and 4th in the 500 free(4:30.04). Mitchell went to NCAAs and swam the mile, 400 IM, and 500 free. He placed 19th in the mile.