The signing of Chavhanga represents a significant coup for the RaboDirect Pro12 strugglers with the 27-year-old being widely regarded as one of the quickest wingers in world rugby.
The Zimbabwe-born speedster has four South Africa caps - including a six-try debut against Uruguay in 2005 - but did not make the squad for the World Cup in New Zealand.
"It's a great signing for the Dragons," said head coach Edwards.
"We wanted a player to further develop our counter-attacking and backfield play.
"We've made no secret that our style of rugby is attacking play and Tonderai's pace and counter-attacking ability really stands out.
"Tonderai's got a great deal to offer the region, not only immediately but also for the future.
"Despite his experience Tonderai's still only 27 and has a great deal of ambition for the game.
"This signing will breathe even more excitement into our squad and our supporters."
And the anticipation Edwards is expecting on the Rodney Parade terraces is an emotion shared by Chavhanga himself.
"I am very, very excited about going to the Dragons," said Chavhanga.
"It's something I've been looking to do for the last couple of years. I've played a few games in the Europe and although it's pretty cold, I'm looking forward to the change."
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