The network announced Thursday that Perry will play the naive, beautiful cousin of Zoey, played by Jennifer Morrison. CBS didn't say when the episode will air.
The series stars Josh Radnor, Jason Segel, Neil Patrick Harris, Alyson Hannigan and Cobie Smulders. It airs Mondays at 8 p.m. ET.
CBS' announcement comes on the heels of Perry picking up two trophies Wednesday at She won as favorite female artist and favorite online sensation.