Mahinmi was born to a Beninese[1] father who helped other Africans immigrate to France and a Jamaican[1] mother who taught in a preschool.

Playing for the Spurs' 2006 summer-league team at Rocky Mountain Revue, Mahinmi demonstrated his athleticism, but had difficulty maintaining rebounding or post position without fouling.

[4] On October 30, 2007, Mahinmi made his NBA debut with the Spurs against the Portland Trail Blazers, playing only 74 seconds and registering no statistics.

[6] Mahinmi averaged 17.1 points and 8.2 rebounds in the NBA Development League, leading the Austin Toros to the D-League Finals in which they lost.

[9] On January 15, 2011, Mahinmi scored a career high 17 points in a loss to the Memphis Grizzlies, going 6–6 from the floor and 5–6 from the free throw line while collecting 6 rebounds.

On March 20, 2011, Mahinmi collected a career-high 13 rebounds and 9 points after playing 20 minutes in the 101–73 win over the Golden State Warriors.

As a result, Mahinmi almost never played in the fourth quarter as teams would intentionally foul him to get extra possessions and limiting the Pacers' Offensive rating.

On February 19, 2016, Mahinmi matched a career high with 19 points and grabbed 11 rebounds in a 101–98 win over the Oklahoma City Thunder.

[15] On March 27, 2016, Mahinmi helped the Pacers defeat the Houston Rockets, tying a career-high 19 points and 11 rebounds in a 104–101 win.

[21] He made his debut for the Wizards on November 26, 2016, against the San Antonio Spurs after missing the first 14 games of the season while recovering from left knee surgery.