Sheckler was born in Orange, California to Randall Sheckler and Gretchen Walsh. He has two younger brothers, Shane and Kane.

Sheckler began skateboarding at four years old, and, in 2003, aged 13 years, Sheckler became the world's youngest professional in the sport. In August 2003, Sheckler competed in the X Games and became the youngest participant ever to have won a gold medal, taking first place in the "SBX Park" event. Sheckler finished the 2003 season ranked first in the world in the "street" discipline, having taken first place in the event at the Gravity Games and third place in the event at the United States Skateboarding Championships.

Sheckler has continued to find success in "park" events, winning two events in 2005 on the Dew Action Sports Tour and, having accumulated the most points over the Tour's five stops and across the Tour's skateboarding disciplines, taking the title of "Athlete of the Year".

Sheckler's performance in "street" events has been mixed; he finished ninth in the event at the 2004 X Games but nevertheless finished 2004 ranked second in the world in the event, having also captured a Gravity Games bronze medal and United States Skateboarding Championships gold. In 2005, Sheckler finished third in the "street" event at the World Championship of Skateboarding in Munster, Germany.

In skateboarding circles, Sheckler is known for the eponymous "Shecklair" move, a combination of a kickflip,stiffy and an Indy air completed with the legs fully extended.

After his breakout 2003 season, Sheckler spent part of 2004 touring with Tony Hawk, appearing with the skateboarding legend on TEENick and traveling to Australia, Canada, and Spain; Sheckler also appeared in two of Hawk's video games, Tony Hawk's Underground 2 and Tony Hawk's American Wasteland. In mid-2004, after leaving primary sponsor World Industries for Almost Skateboards, Sheckler appeared in the company's August 2004 video, Almost: Round Three. On television, Sheckler appeared on the February 10, 2005 episode of MTV Cribs

Almost Skateboards is Sheckler's core sponsor. Additional sponsors include Etnies, Oakley, Red Bull, Volcom, Kicker Audio, CCS Magazine, Silver Trucks, and Amp'd Mobile. In his nascent MotoCross career, he is sponsored by Classic Honda and AlpineStars.