After going undrafted in the 2016 NBA draft, McClellan signed with the Washington Wizards on September 23, 2016. He made his debut for the Wizards in their season opener on October 27, 2016, recording seven points and two steals in four minutes off the bench in a 114–99 loss to the Atlanta Hawks. With starting shooting guard Bradley Beal out injured on November 12, 2016 against the Chicago Bulls, McClellan made his first career start and subsequently scored a season-high 15 points in a 106–95 loss. On December 6, 2016, he was assigned to the Delaware 87ers of the NBA Development League, pursuant to the flexible assignment rule. On December 18, 2016, he was recalled by Washington. On April 4, 2017, he was assigned to the Rio Grande Valley Vipers. He was recalled by the Wizards a week later.