At the 2017 World Championships in Helsinki, Fernández set a new personal best in the short program, in which he successfully executed all the jump elements (a quad-triple toe loop combination, a quad Salchow and a triple Axel), three level four spins, and received maximum grades of execution from every judge for the step sequence. He received 109.05 points in the short program to take the lead, the third highest mark ever at the time of the event. Fernández started his free skate a quad toe loop, quad Salchow-triple toe loop and triple Axel-double toe loop, but fell on another quad Salchow attempt, doubled a planned triple flip and stumbled on the landing of the triple loop to finish 6th in the segment, dropping him to 4th place overall. It was the first time off the podium at a World Championships since 2012.