Cunha, who is Brazil Under-23s' all-time leading goalscorer, joins Diego Simeone's side on a five-year deal and will provide capable support to talisman Luis Suarez up top.
Speculation had linked the 22-year-old to Everton, Atalanta and Napoli, but the reigning LaLiga champions swooped in to secure his services after a move for Dusan Vlahovic fell through.
Cunha initially moved to Europe to play for Swiss side Sion, subsequently joining RB Leipzig before finding a new home with Hertha in 2020.
Last term, the versatile attacker scored eight and assisted six across 28 games in all competitions, leading Hertha's charts ahead of second-place Dodi Lukebakio with 12 goal involvements.
The Brazil striker created 54 chances - 18 more than closest team-mate Vladimir Darida – putting him sixth among forwards playing in Germany.
Solely in the Bundesliga, the former Leipzig man has improved in front of goal in every campaign since 2018-19 and most recently scored a career-high seven goals in the German top-flight, finding the target with 62.5 per cent of shots.
Similarly, Cunha almost doubled his touches in the opposition box in such fixtures last year, producing 98 in comparison to 53 last term and 58 the year before.
However, it is in terms of dribbling where Atletico's new man comes to the fore.
Since his arrival in Berlin on January 31, 2020, only five forwards across Europe's top-five leagues have completed more dribbles than Cunha's 123 – successful in just over 60 per cent of all dribbles he attempted.
No player in the Bundesliga can match that dribbling tally while Yannick Carrasco is the only Atletico player to have completed more than 100 dribbles in the same time frame.
Cunha will likely be tasked with partnering Suarez as a second striker, perhaps replacing the in-form Angel Correa as Los Colchoneros go in search of back-to-back LaLiga titles.
Makeshift forward Correa has scored eight goals in his last 10 across all competitions - including three in his last two - for Simeone's men, having previously netted seven times in his last 73 for the club.
Cunha could feature as early as Sunday against Villarreal for the defending Spanish champions, who have started a new campaign with consecutive wins for the fourth time during the Simeone era.