The former American Idol contestant was photographed playfully kissing and hugging actor Elyes Gabel on the set of their new CBS show, Scorpion.
McPhee, 30, filed for divorce from husband Nick Cokas in May – months after she was caught locking lips with her Smash director, Michael Morris.
Though McPhee and Cokas were reportedly separated at the time, Morris is married to actress Mary McCormack, with whom he has three daughters.
Gabel, 31, is a British star who is also slated to appear in the sci-fi thriller Interstellar with Matthew McConaughey, Anne Hathaway and Jessica Chastain.
McPhee's rep had no comment on the photo.