Los Angeles Superior Court Judge Reva Goetz approved the stay-away order on Monday after attorneys for Rooney sought protection for the Academy Award-nominated actor, claiming he lives in fear of stepson Chris Aber.
The order requires Aber to stay 100 yards away from Rooney and his home and to refrain from contacting the actor until a hearing on Feb. 24, when the restraining order may be extended.
"Chris is verbally abusive toward Mickey," the court filing states. "He yells and screams at Mickey. He threatens, intimidates, bullies, and harasses Mickey.
"Mickey is effectively a prisoner in his own home," the filing states.
It accuses Aber of forcing Rooney to make certain personal appearances, and has required him to sign financial documents without reading them.
Attempts to find a working phone number for Aber were unsuccessful.
The actor's attorneys also obtained a temporary conservatorship for Rooney to protect his personal and financial interests. The order allows the attorneys to secure Rooney's financials assets and obtain control of his website and any financial documents in Aber's possession.
Rooney is described in a news release about the case as still being sharp-witted.
"All I want to do is live a peaceful life, to regain my life and be happy," Rooney wrote in a statement. "I pray to God each day to protect us, help us endure, and guide those other senior citizens who are also suffering."
Rooney's film career spans more than eight decades and he received four Academy Award nominations and an honorary Oscar. In the 1930s and 40s, he played Andy Hardy in a series of films, and received his first Oscar nominations in 1939 for "Babes in Arms" and in 1943 for "The Human Comedy."