About 400 volunteers scoured the city's streets, alleys and other refuges of the homeless Thursday night, the San Francisco Chronicle reported.
There were similar counts in dozens of other U.S. cities and counties this week -- required by the federal Department of Housing and Urban Development to set funding levels.
"Everyone is trying to figure out how to do better," Mayor Ed Lee told volunteers as they set out. "As good as we've been doing as a city, we want to do better."
Newsom, who is now lieutenant governor of California, released figures showing he got 12,210 people off the streets in his seven years as mayor, including 5,158 sent away with free bus tickets.
San Francisco's last count two years ago found a homeless population of 6,514, but only 2,709 of them were actually sleeping on the streets. The count includes residents of jails, shelters and treatment centers.