Öncü continued with Tech3 for the 2021 season, and he achieved his first Moto3 podium with a 3rd place finish in Barcelona, followed by two 2nd places in Austria and Aragon. He also scored his first Pole Position in Austria, but had to start from the back of the grid, because his Tech3 team elected to switch him to slick tyres, and finished just seconds after the three-minute board was shown. After the race in Austin, he was given a two race ban, after being deemed to have caused a massive incident involving clipping Jeremy Alcoba's front wheel, who went tumbling across the track, his bike being struck by Andrea Migno and Pedro Acosta, who both went airborne. Luckily all riders involved miraculously walked away from the incident unscathed, and Öncü was replaced by Daniel Holgado for the two race ban. Deniz finished the season with three podiums, 11th in the championship standings, and 95 points.
