The Twin Peaks star will play socialite Greer Sheridan on the CW drama, according to TV Line.
A former close friend of Siobhan (Sarah Michelle Gellar), Sheridan will run into her twin sister Bridget (also Gellar) at a charity event.
Still posing as Siobhan, Bridget will work to discover what ruined the relationship between her sister and Sheridan.
Amick has previously played recurring roles on Gossip Girl, Damages and CSI: NY. She has also appeared in episodes of White Collar, Californication and ER.
Ringer continues on Tuesdays at 9/8c on The CW. Sky Living airs the show on Thursdays at 8pm in the UK.
> Sarah Michelle Gellar 'loves Ringer plot twists'
> Ringer: 'The Poor Kids Do It Everyday' recap
Watch a clip from Tuesday night's Ringer below: