The collision was reported at 8:08 a.m. at Market and Castro streets.
A man riding a bicycle was traveling south on Castro Street and was crossing Market Street when he struck a 72-year-old man walking east in a crosswalk, police spokesman Sgt. Daryl Fong said.
Both the bicyclist and pedestrian were taken to San Francisco General Hospital. The bicyclist's injuries were not life-threatening, he said.
Witnesses reported that the bicyclist may have run a red light prior to the collision, but that information has not yet been confirmed, Fong said.
"Investigators are still trying to determine the right-of-way of the parties involved," he said.
Anyone who may have witnessed the accident is encouraged to call the Police Department's accident investigation bureau at (415) 553-1641.