The former actor was initially charged with first-degree murder in the death of Joshua Sutter.
Medina's attorney, Stanley L. Friedman, said his client agreed to plead to the lesser charge rather than risk a murder conviction and a possible life sentence.
Superior Court Judge Daviann L. Mitchell sentenced Medina after hearing emotional testimony from Sutter's family members who gathered in her Lancaster, California, courtroom.
"Put this killer in general (prison) population so he will see and feel the same fear that Joshua must have felt," the 36-year-old victim's father, Donald Sutter, said in a voice filled with emotion.
Medina stabbed Joshua Sutter to death on Jan. 31, 2015, following an argument in the home the two shared in Green Valley, a mountain town north of Los Angeles.
Friedman said the argument, over Medina's girlfriend, began in the kitchen and that she and Medina fled to his bedroom and locked the door when it became heated. When Sutter broke through the door, Friedman said, Medina stabbed him with a sword he kept in the room.
Medina played the Red Lion Wild Force Ranger on "Power Rangers Wild Force" in 2002. He was the voice of Deker on "Power Rangers Samurai" in 2011 and 2012 and also appeared in such shows as "ER" and "CSI: Miami."
Sutter's father told the judge no one would look at Medina as a celebrity again.