The Black Swan actress is said to have rushed to the man's side at her home in Los Angeles after he suffered a violent seizure, reports TMZ.
The 50-year-old man was reportedly working at the star's house when he started choking, coughing up blood and vomiting, and also bit through his tongue.
The actress grabbed the man's head and told her friend to call 911, before she put his wallet in his mouth to stop him swallowing his tongue.
Paramedics soon arrived to take the man to a nearby hospital, where Kunis asked to ride with him in the ambulance, but was told that it wasn't necessary.
The man reportedly made a full recovery after receiving treatment.
The incident happened a day after Kunis's alleged stalker was arrested for violating his restraining order against her.
Last month, Mila Kunis dismissed rumours that she is dating her former That '70s Show co-star Ashton Kutcher.