The partnership began in September and quickly obtained good results: five Challenger finals in a row, with two runners-up (Cali and Quito) and three titles (Campinas, Rio de Janeiro, and Porto Alegre).

In June 2013, he participated for the first time in a Grand Slam at the 2013 Wimbledon Championships with compatriot André Sá, losing in the first round to the Bryan brothers, the No.

[1] In 2017, he reached the third round of the Australian Open and got three more runner-ups on the ATP 250 level in São Paulo, Lyon and Chengdu alongside Marcus Daniell.

In the South American swing (clay), they won the Córdoba Open defeating Argentines Leonardo Mayer and Andrés Molteni in the final.

In October, they were runner-ups St. Petersburg Open losing to the number 2 seeded pair, Austrian Jürgen Melzer and Frenchman Édouard Roger-Vasselin.

[5] In grass season, he won his fourth ATP 250 title at Stuttgart Open defeating Uruguayan Ariel Behar and Gonzalo Escobar from Ecuador.

Nine months after his surgery, Demoliner returned at an ATP Challenger Tour event Brawo Open in Germany where partnering Jan-Lennard Struff he won the title.

Using a protected ranking at the US Open, he reached a Grand Slam quarterfinal for the first time in his career with his partner Joao Sousa, having never passed the third round at a Major.

[9] At the 2023 Pan American Games, playing in doubles, Demoliner and Gustavo Heide overcame the hostile Chilean crowd and took gold.