The 21-year-old will make his F1 debut next season on the 30th anniversary of his father's own debut at the 1991 Belgian Grand Prix. The test took place in Bahrain in early April and, unusually for a the desert circuit, was partly rained off.
He had a hard first season in the category, winning one sprint race and finishing 12th, but he has demonstrated significant progress this season.
Mazepin now lies third in the F2 standings with just this weekend's finale on Bahrain's outer circuit to come, having won feature races at Silverstone and Mugello.
The young German, a member of the Ferrari Driver Academy, got his first taste of the pace of an F1 vehicle in April previous year by taking part at in-season testing for the Scuderia and Alfa Romeo.
The German said he was left speechless by the deal and thanked Haas and Ferrari for their trust. I know that I owe them everything.
Team boss Gunther Steiner added: "I'm excited to see what Nikita can achieve in Formula 1 and we look forward to giving him the opportunity to compete at the highest level of world motorsport". "And this year's field has undoubtedly been one of the most competitive in recent seasons".
He added: "Mick has won races, collected podiums and excelled against some pretty exceptional talent in 2020".
After a quiet first season, Schumacher won eight races in 2018, beating then-Red Bull junior Dan Ticktum to the championship with the Prema team he now races with in Formula 2.
"We have an opportunity ahead of us, as a team, to evaluate and nurture a new driver given our familiarity with our race package heading into 2021", Steiner said.
"We are putting in place our building blocks for the continued long-term growth of the team and I look forward to Mick's contributions both on and off the track in that process".
Schumacher has tested out both a Scuderia Ferrari and an Alfa Romeo Racing ORLEN before but now has come his time to finally race a F1 vehicle. This year he was scheduled to drive for Alfa in FP1 at the Eifel GP, but the day's activity was rained off.
While he has completed only one public test day in a current auto with the Brackley outfit - at Barcelona in May previous year - Mazepin has been running extensively in two-year-old models at various circuits around the world, including most recently Bahrain and Abu Dhabi.
"It is unbelievable to be racing in the same sport as he did", said Schumacher Jnr on Wednesday.