The Oscar winner's publicist, Alan Nierob, said Gibson has been in the Central American country for several days working with Mending Kids International, a children's charity.
Nierob said Gibson is spending more time working in Guatemala than the 16 hours of community service that a plea deal calls for him to perform.
Gibson pleaded no contest in March to a misdemeanor charge for striking former girlfriend Oksana Grigorieva during a January 2010 fight, but did not admit guilt.
A judge approved his working with the charity, which the actor-director's estranged wife, Robyn Moore Gibson, once led. Mending Kids provides free surgery for children with cleft lips or spina bifida, a disorder in which the spinal canal and backbone don't close prior to birth.
Gibson, who wore a purple T-shirt with Mending Kids logo, said he has been coming to Guatemala the past 15 years to support the charity.
He spoke to reporters on the condition of not answering questions about his personal life. He is currently in a custody battle with Grigorieva.
