The incident occurred late last night when Sanjay (40) returned home in an inebriated condition and raped his mother, Superintendent of Police West Harish Chandra said.
After the alleged incident took place, the victim raised an alarm following which the neighbours rushed in and rescued her by locking the accused, he said.
The neighbours beat up the accused and informed his sister and the police, he added.
The accused was arrested after his sister lodged an FIR against him, the SP said, adding the victim has been sent for medical examination.