At the 2014 Commonwealth Games in Glasgow, Horton won the silver medal in the 1500 metre freestyle in new junior world record time of 14:48.76 and narrowly missed the podium in the 400-metre freestyle finishing in fourth place in 3:44.91. In the 4 × 200-metre freestyle relay event, Horton alongside Thomas Fraser-Holmes, David McKeon and Ned McKendry finished as the fastest qualifies with Horton swimming the anchor leg in 1:49.17. In the final, Horton was replaced by Cameron McEvoy and they went on to win the gold in a new games record time of 7:07.38.