The Baltimore Ravens selected Madubuike with 71st overall pick in the third round of the 2020 NFL Draft.

[11] He missed the first four games of the season after suffering a knee sprain late in training camp.

[15] In Week 16 against the New York Giants, Madubuike recorded his first career sack on Daniel Jones during the 27–13 win.

[18] He recorded another sack in the Ravens' 30–31 Week 15 loss over Green Bay Packers.

[30] Three days later, on March 8, the Ravens signed Madubuike to a four-year, $98 million contract extension.

[31][32] Madubuike went by his English first name Justin, which is written on his birth certificate, from elementary school until 2024.

During the 2024 offseason, he opted to switch to his Nigerian name Nnamdi in recognition of his heritage.