One of Symonds' biological parents was of West Indian background and the other was believed to be of Danish or Swedish descent. Symonds' adoptive parents Ken and Barbara moved to Australia shortly after his adoption, when he was three months old. Of the adopted siblings, Louise Symonds participated in Gladiators. He also has two non-adopted siblings. He spent the early part of his childhood in Charters Towers, northern Queensland, where his father Ken taught at the private fee paying All Souls St Gabriels School, which Andrew attended. He showed sporting prowess from a very early age. "Dad was cricket mad. He’d throw balls to me five or six days a week, before school, after school. And we’d play all sorts of games inside the house with ping-pong balls and Christmas decorations." Much of his junior cricket was played in Townsville for the Wanderers club, father and son making the 270-kilometre return trip sometimes twice a week. The family later moved to the Gold Coast, where his parents were on the staff of All Saints Anglican School in Merrimac. Symonds was a student at the school.

Symonds is an aggressive right-handed batsman who can also bowl off spin or medium pace, making him a good all-rounder. He is an exceptional fielder, with a report prepared by Cricinfo in late 2005 showing that since the 1999 Cricket World Cup, he had effected the fifth equal most run-outs in ODI cricket of any fieldsman, with the fourth highest success rate., with Ricky Ponting putting him the best fielder he has seen, and a better and more versatile one than Herschelle Gibbs and Jonty Rhodes because Symonds is taller than them, giving him better defensive coverage range and has greater throw power outside the circle. He is very agile for his size and weight (medium-heavy build; 187 cm tall), has excellent reflexes, is able to take catches well and has a powerful and accurate throwing arm. His nickname is Roy, shortened from the name Leroy, after a coach from early in his career believed he resembled local Brisbane NBL hero Leroy Loggins.