Main •
Jang Ki-yong as Shin Woo-yeo :A 999-year-old
Gumiho who wants to become a human. •
Lee Hye-ri as Lee Dam :A college student born in 1999 who accidentally swallows a fox bead and has never been in a relationship before. •
Kang Han-na as Yang Hye-sun :Shin Woo-yeo's slow-witted friend who is a romance expert. She used to be Gumiho for 700 years, but has now turned into a human. •
Kim Do-wan as Do Jae-jin :Dam and Soo-kyung's man who develops a romantic relationship with Yang Hye-sun after being dumped by his ex-girlriend.
Supporting •
Bae In-hyuk as Gye Sun-woo :Lee Dam's senior in college who is a ladies' favorite. He develops interest on Lee Dam because she keeps on avoiding him. Later they also get tied by a red thread of destiny but eventually it cuts off as Sun-woo leaves the country for higher study. •
Park Kyung-hye as Choi Soo-kyung :Lee Dam's and Do Jae-jin's best friend. •
Choi Woo-sung as Lee Dan :Lee Dam's younger brother •
Kim Do-yeon as Gye Seo-woo :Gye Sun-woo's younger sister. •
Kim Kang-min as Jung Seok :Lee Dam, Choi Soo-kyung and Do Jae-jin's senior. •
Bang Eun-jung as Jeon Da-young
Special appearances •
Lee Kyu-sung as Mountain Spirit Transformation •
Jung So-min as Seo-hwa : The woman Shin Woo-yeo loved in the past and left a lasting impression. She was his first love who lost her life because of the fox bead Woo-yeo transferred into her. •
Kim Eung-soo as Shin Woo-yeo's transformation (ep. 1) •
Han Ji-eun as leader of publishing company (ep. 1, 5–6) •
Go Kyung-pyo as
Sansin, a mountain spirit that watches over Shin Woo-yeo and Lee Dam (ep. 7, 10, 11, 13, 14) •
Jang Sung-kyu as Lee Dam's blind date and Do Jae-jin's senior who appears in Episode 6. He is an arrogant man who looked down on Lee Dam during their first meet and fell down on the floor due to Shin Woo-yeo's magic. •
Oh Hyun-kyung as Kim Hyun-kyung (ep. 6) : Lee Dam and Lee Dan's mother who works as a fashion magazine editor. •
Kang Mi-na as Choi Jin-ah (ep. 8, 11) : Do Jae-jin's ex-girlfriend. •
Son Seong-yoon as Seo Young-joo, a professor of ancient history at Seogwan University •
Lee Jun-hyuk as Professor Park Bo-gum : A professor who is known for his rigor in the history department. •
Oh Jung-se as Do Jae-gang, Jae-jin's brother •
Shim Hyung-tak as Gye Sun-woo's uncle who owns a restaurant ==Production==