The former Spice Girl will replace Marissa Jaret Winokur, another Dancing with the Stars alum who served as the reality series' first season host last summer.
"We are so happy to welcome Mel B to the Oxygen family," said Oxygen programming executive Amy Introcaso-Davis. "Her commitment to health and fitness inspires the people around her and captures the core essence of a show like Dance Your Ass Off."
A cross between Dancing with the Stars and The Biggest Loser,Dance Your Ass Off follows overweight contestants as they're paired with professional dancers who train them for weekly routines that they then perform in front of a live studio audience and judging panel.
The judges score the dance routines before the contestants weigh-in to reveal their weekly weight loss total -- with both being combined for an overall score that determines who is eliminated at the end of each episode.
Oxygen renewedDance Your Ass Off for a second season in November after its first season averaged more than one million total viewers -- making it the most-watched freshman series in the network's history.
"After the birth of my second daughter, I wanted to find a fun and effective way to drop the pounds and get back in shape," said Mel B.
"I realized I didn't have to look far to find the answer. Whether I was dancing around the house with headphones on, on stage with the Spice Girls, working on my high energy fitness DVD, or performing eight times a week in my Las Vegas show, I learned firsthand that dancing was the key to shedding off the pounds and keeping them off. I'm excited and looking forward to teaming up with Oxygen to cheer on the contestants as they dance their pounds off."