John Michael Finley was born in Jonesboro, Arkansas and raised in Lebanon, Missouri. He is the second of five children born to Wayne and Betsy Finley. He began singing and acting in Junior High. He attended Roosevelt University's Chicago College of Performing Arts and began his professional acting career in Chicago and surrounding areas. His stage credits include Chicago theaters such as Lyric Opera of Chicago, Paramount Theatre, Marriott Theatre, Drury Lane Theatre, Writers' Theatre, Court Theatre, and Mercury Theatre.

Finley moved to New York City in 2015 where he made his Broadway debut in the ensemble of Les Miserables and as the understudy for Jean Valjean. I Can Only Imagine is his first film. Following completion of I Can Only Imagine, Finley returned to Broadway as the Standby for Elder Cunningham in The Book of Mormon.

In 2018, Finley made his West End debut in the role of Elder Cunningham in The Book of Mormon. That year, he made his big screen debut as Christian singer-songwriter Bart Milland in I Can Only Imagine, for which he received acclaim. He will reprise this role in the 2026 sequel.