The flanker, who formed part of the Springboks team that secured a series success over the British and Irish Lions in 2009, boasts a wealth of experience after spending much of his career with the Cheetahs in his homeland.
The 31-year-old, who currently plays for Japanese outfit Docomo Red Hurricanes, is looking forward to teaming up with Northampton at the start of next year.
"I feel humbled to be afforded the opportunity to join a club with such a rich history and traditions," said Brussow.
"Franklin's Gardens is one of those special places you hear some of the best players in the world talk about and the thought of representing a team like Northampton Saints is something that excites me immensely."
Saints director of rugby Jim Mallinder believes Brussow will be a great asset to his side as his vast quality and experience will benefit the entire squad.
"Heinrich has shown his class year in, year out, and we're delighted that he has decided to join us," Mallinder said.
"He has plenty of experience and our younger players will learn a lot from him, especially from his play at the breakdown."
Northampton are currently ninth in the Premiership after bouncing back from an opening defeat to Saracens with victory over Leicester Tigers last time out.