Just before 10 a.m., the woman, who lives in the 1900 block of Arbor Avenue, reported that a man wearing a black shirt was photographing her through the partially open window.
The woman told police the man fled when he realized she knew he was there.
Officers contacted a neighbor, Evan Chieda, 36, whom they then arrested without incident on a misdemeanor charge of secretly photographing a person who is fully or partially undressed.
Police said there is no indication that Chieda has been involved in any other similar incidents, but they are checking with other Peninsula law enforcement agencies.
Anyone with information about Chieda or similar incidents he may be involved in is encouraged to call Belmont police at (650) 595-7400 or the crime tip line at (650) 598-3000.