The players will join coaches and staff at "The Window," a drop-in services hub run by the Cathedral Basilica of St. Joseph's Office of Social Ministry, 49ers spokeswoman Lisa Goodwin said.
The center provides food, walk-in medical services, transitional shelter and job counseling to homeless men, women and families in San Jose.
There will also be an arts and crafts area where homeless and foster kids will be able to play and work on art projects with the players, Goodwin said.
About 150 people are expected to attend today's event.
A volunteer who answered the phone at the social ministry this morning said everyone getting ready for the event was "pretty excited."
The event is scheduled to take place from noon to 2 p.m. at The Window, located across the street from the Cathedral Basilica of St. Joseph at 80 S. Market St.