Dortmund kept pace with Bayern Munich at the league summit having seen the leader thrash Hoffenheim 4-0 in its match at Allianz Arena.
Marco Rose's side came into the game without top scorer Erling Haaland, who has against been sidelined, this time for a couple of weeks with a hip injury, while Raphael Guerreiro, Gio Reyna, Thomas Meunier and Mo Dahoud were also among the team's absentees.
That may have given Bielefeld confidence it could pull off a surprise result and indeed the home side started well, a compact defence giving Dortmund little opportunity to break through.
Bielefeld produced the game's first two best openings, first for Alexander Hack, whose shot on the turn was well saved by Gregor Kobel, before Anni Serra robbed Marin Pongracic of the ball and bore down on goal, only for Kobel to get the better of him, too.
Those misses would prove costly, as Emre Can soon put Dortmund in front, converting from the penalty spot after Donyell Malen had been fouled.
Hummels then gave his side a two-goal cushion with a sublime volley from the edge of the box on the stroke of half-time.
Bielefeld again tried to put Dortmund under pressure as it sought a way back into the match after the break.
Veteran forward Fabian Klos tested Marwin Hitz, who had replaced Kobel in Dortmund’s goal, while Bundesliga debutant and fellow substitute Guilherme Ramos almost pulled a goal back within moments of entering the pitch but headed wide from a corner.
Patrick Wimmer then drew a fine reflex save from Hitz as Rose’s men struggled to make any kind of attacking impact, but as in the first 45 minutes, Bielefeld’s lack of a cutting edge would come back to haunt it.
There appeared to be little danger when Marco Reus collected a high ball on the left-hand edge of the box and played it back to Bellingham. The 18-year-old had other ideas, though, and dribbled past three defenders before executing a sublime chip over Stefan Ortega to put his side 3-0 up and effectively seal the victory.
Klos pulled a goal back from the penalty spot late on after Hummels had fouled Wimmer, but the result was never in doubt as Dortmund returned home with all three points.