Frisby, 24, has played 54 Super Rugby games, while he made his Wallabies debut last year.
The scrum-half, who has made five appearances for Australia, said he still had plenty he wanted to achieve with Reds.
“Ballymore has been home for a long time and it’s somewhere I’ve made a lot of great memories, so I’m really pleased to know my future is here for at least another couple of years,” Frisby said.
“I feel like I’ve still got a lot to achieve in the Reds jersey.
“The guys have worked incredibly hard over the pre-season and we’re really looking forward to the season.”
Reds head coach Nick Stiles said he expected even further development in Frisby’s game.
“Nick joined the Reds six years ago and has grown immensely as a player in that time, but we feel strongly that his best years are still ahead of him,” he said.
“He’s a talented athlete, as shown through his selection for the Wallabies last year, but we’re looking forward to him continuing to grow as a leader within the group.”
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