Facebook's Menlo Park headquarters was spattered with posters and banners proclaiming #GlobalCausesDay on April 28.

In its third year, Facebook's Global Causes Day is an opportunity for Facebook employees to "flex our altruistic muscle as a community," said Tudor Havriliuc, a Facebook vice president.

Over the course of the day, about 4,000 Facebook employees at its 30 offices around the world worked on volunteer projects with about 500 nonprofits, said Ime Archibong, Facebook director of strategic partnerships.

In Menlo Park, from 1,500 to 2,000 employees helped assemble roughly 3,000 snack packs for kids from low-income families; 700 backpacks for students in the Ravenswood City School District in East Palo Alto and Belle Haven; and 800 care kits for refugees in Greece. Some nonprofits also received social media training at Facebook that day.

In Menlo Park, Facebook worked with about 15 local nonprofits, said Susan Gonzales, director of community engagement at Facebook. They have ongoing partnerships, she said. At the April 28 event, volunteers helped paint, landscape and assemble furniture at the Boys & Girls Clubs of the Peninsula in Menlo Park and at Street Code and Live in Peace in East Palo Alto.

About a year ago, said Ms. Gonzales, Facebook launched a program called Clubs for Causes, which enables employees who have interests in a particular cause to create a club and receive support to work on that cause. Now, there are about 30 clubs, a Facebook spokesperson said.

Mr. Havriliuc said that as a Facebook human resources executive he wants to "make sure that people who work here find some amount of meaning and empathy in their day-to-day jobs." Personally, Mr. Havriliuc said, one cause he cares deeply about is LGBTQ rights. He said he grew up gay in Romania, where being gay could result in incarceration.

At a booth on the garden rooftop at Facebook, employees packaged snack packs that will be distributed by Second Harvest Food Bank to supplement weekend meals for kids from low-income families, said Alisa Tantraphol, associate director of strategic partnerships at Second Harvest Food Bank. The snack packs are the result of a fundraising initiative called "Stand up for Kids" that is co-chaired by Sheryl Sandberg, Facebook's chief operating officer and a Menlo Park resident.

Childhood hunger can lead to kids' behavior difficulties, anxiety or mood swings, and can make it harder for kids to learn. "Those challenges affect all of us and have the potential to rob our future workforce of great minds," Ms. Sandberg said. "There are so many things about the world we can't change this is something we can."

The day opened with a talk by hip-hop artist and actor Common, who told of the organization he founded, Common Ground Foundation, which promotes education, creative arts and job readiness for underserved youth in Chicago, said a Facebook spokesperson.

The day concluded with a talk by Iranian-born British American actress Nazanin Boniadi, who has appeared in TV shows "Homeland," "How I Met Your Mother" and "Scandal" and is the female lead in the upcoming film "Ben-Hur," scheduled for release in August. She talked about her work with Amnesty International in its efforts to release political prisoners and prisoners of conscience in Iran. She is on the board of directors of the International Campaign for Human Rights in Iran.