At the 2016 Rio Olympics, Mayer earned a silver medal with a new personal best of 8834 points, finishing behind only two-time gold medallist Ashton Eaton, who was the world record holder at the time. Highlights of his campaign include equalling or improving personal outdoor bests in four events (100 m, shot put, 400 m, pole vault) and performing seasonal bests in three others (long jump, high jump, 1500 m); he was also the best decathlete in two disciplines (the shot put, with 15.76 m and 836 points; and the pole vault, with 5.40 m and 1035 points, sharing first place with Thomas van der Plaetsen) and lead the standings at the end of the first day of the competition (i.e. after 5 out of 10 events). Furthermore, this performance ranks as the sixth-best personal best score in the men's decathlon, and showed a marked improvement in form for Mayer, bettering his former personal best of 8521 points (set during the aforementioned silver medal run at the 2014 European Athletics Championships) by 313 points and the French national record by 260 points.