A product of Inter Milan's youth academy, Dimarco debuted for the club on 11 December 2014, at age 17, entering as a substitute for Danilo D'Ambrosio in the 84th minute of a goalless draw away to Qarabağ in the group stage of the UEFA Europa League, with his team having already advanced.

[4] Dimarco made his Serie A debut on 31 May 2015, replacing Rodrigo Palacio in the 89th minute of a 4–3 win over Empoli in the season finale.

[6] On 6 February, Dimarco made his debut for Ascoli in Serie B in a 0-0 home draw against Latina, he was replaced by Dario Del Fabro in the 81st minute.

[24] On 12 November 2023, in a Serie A match at home to Frosinone, Dimarco scored from 56.08 m, near the half-way line; the game ended in a 2–0 victory for Inter.

[26] In 2013, Dimarco was a member of the Italy under-17 side that finished runners-up at the UEFA European Under-17 Championship in Slovakia and was eliminated in the second round of the FIFA U-17 World Cup.

He is known in particular for his pace, tireless running, eye for goal, and his powerful and accurate shot from outside the penalty area, as well as his ability to interpret the game; he is also a threat from set pieces.

[34] Considered by journalist Emmet Gates to be one of the best full-backs in Serie A, Dimarco's pace and technical ability allow him to excel as a left-sided wing-back in a 3–5–2 formation, where he is able to overlap and get forward with his attacking runs, both on and off the ball, to create chances for his team with his crossing.

Dimarco's defensive ability has been cited as a weakness in his game by journalist Kyle Bonn of The Sporting News.