The service was held Saturday at the Ramona Bowl Amphitheater.
MacKenzie and 18 other firefighters died on June 30 when they were overrun by the Yarnell Hill Fire near Phoenix.
An avid snowboarder, MacKenzie grew up in California's San Jacinto Valley, where he was a 2001 graduate of Hemet High School and a former member of the town's fire department.
He joined the U.S. Forest Service in 2004, then transferred two years ago to the Prescott Fire Department, longtime friend Dav Fulford-Brown told The Riverside Press-Enterprise.
MacKenzie, like at least one other member of the Granite Mountain Hotshots, had followed his father into firefighting.
The victim's remains arrived home Wednesday along with those of 21-year-old firefighter Kevin Woyjeck of Seal Beach. Woyjeck's funeral will be held Tuesday morning in Long Beach.