P Babu Rao was visiting his younger brother's house in Musidipalle village of the district when he allegedly tried to sexually harass his sister-in-law, Srungavarapukota Circle Inspector S Laxmana Murthy said.
An argument broke out between them following which he stabbed her using a sharp object which he then used to kill himself, Murthy said.
The 23-year-old victim sustained serious injuries in the attack and was shifted to King George Hospital in Visakhapatnam, police said.
A case of attempt to murder under section 307 of IPC has been registered in connection with the incident, police added.