Main •
Park Gyu-young as Han Hae-na/Mak-soon: a high school Korean language teacher who turns into a dog when she kisses someone for the first time. •
Cha Eun-woo as Jin Seo-won/Soo-hyun: a high school math teacher who is afraid of dogs due to childhood trauma. •
Lee Hyun-woo as Lee Bo-gyeom/San-sin: a high school Korean history teacher who is known for being handsome and for his sweet gestures. • Yoon Hyun-soo as Choi Yul: Seo-won's nephew and Hae-na's student. •
Kim Yi-kyung as Min Ji-ah: a high school student.
Supporting Hae-na's family • Ryu Abel as Han Yoo-na: Hae-na's older sister. •
Jung Young-joo as Shin Mi-seon: Hae-na's mother. • Kim Hong-pyo as Han Pan-dong: Hae-na's father. • Song Young-ah as Cheon Song-yi: a music teacher. • Yoo Seung-mok as the vice principal • Kang Soo-bin as Kwon Ri-ae, a schoolgirl who is big fan of Bo-gyeom and good at math as well as physics. •
Shim Wan-joon as a physical education teacher at Garam High School. • Park Hae-in as Yoon-ji: a fellow teacher at Garam High School.
Special appearance • Lee Yong-nyeo as Popi's owner ==Production==