In 2009, Wilder ran for 1,004 yards and 15 touchdowns, while registering 136 tackles (66 solo) and 19 quarterback sacks on defense. He was named the High School Junior of the Year by Rivals.com, as well as 2009 USA Today All-American. Wilder was selected to play in the 2011 U.S. Army All-American Bowl.

Wilder attended Florida State University from 2011 to 2013. He selected Florida State over the University of Florida and the University of Georgia. In 2012, Wilder had a breakout season, running for 635 rushing yards (5.8 yards per carry) and 13 touchdowns. Wilder won Offensive MVP for the 2012 ACC Championship Game. In 2013, Wilder averaged 7 yards per carry. Wilder was named All-ACC Honorable Mention.

On May 12, 2014, Wilder was signed as an undrafted free agent by the Cincinnati Bengals. On August 30, 2014, he was waived by the Bengals. He was signed to the Bengals’ practice squad after clearing waivers. On January 14, 2015, Wilder signed a reserve/future contract with the Bengals. On September 5, 2015, he was waived by the Bengals. On the following day, he was signed to the Bengals’ practice squad.

His father James Wilder Sr. was an NFL running back for the Tampa Bay Buccaneers. In January 2014, James Wilder launched his clothing line, I Am Wilder Apparel. Wilder Jr. and Wilder Sr. also announced that they would be opening and lending their names to a training facility in Tampa Bay, which help prompt Wilder’s decision to retire, stating, “I have a lot of tread on the tires, but it’s a decision I have to make right now.”

On January 20, 2016, Wilder signed a reserve/future contract with the Buffalo Bills. On September 2, 2016, he was waived/injured by the Bills. He was then placed on injured reserve. He was released by the Bills on September 27, 2016.

Wilder signed with the Toronto Argonauts on March 14, 2017, reuniting head coach Marc Trestman with the family, as Trestman was a former Tampa Bay Buccaneers assistant coach when Wilder’s father was a running back on the team. Following an injury to starting running back Brandon Whittaker, Wilder made his first professional start on July 24, 2017 against the Ottawa Redblacks. Wilder took over the starting running back role in September, earning consecutive player of week honors in weeks 13 and 14, gaining 257 and 218 yards from scrimmage in each game, respectively. He amassed 872 yards and 5 touchdowns on 122 carries, as well as 467 yards on 51 catches, and was named the CFL’s Most Outstanding Rookie on November 23, 2017. While largely contained in both playoff games the Argonauts played in, Wilder rushed for a touchdown in the final game of the year, helping Toronto secure a Grey Cup championship.

Wilder has also participated in activism. He was a frequent protester in Houston during Black Lives Matter demonstrations following the killing of George Floyd. Wilder also started the #RunWILDERForACure hashtag once he assumed the starting tailback role in 2017, challenging other CFL running backs to donate a dollar for every yard they gained and $100 for each touchdown they scored towards breast cancer research. Several NFL rushers also joined in the initiative. Wilder participated during all three seasons he played in the CFL.

In late January 2018 Wilder announced that he was planning to sit out of the Argos’ 2018 season in the hopes of pursuing a return to the NFL in 2019. Wilder noted that his current contract of $56,000 (around US$45,000) in 2018, combined with the risk of career ending injury, does not give his family comfort about the future were he to play in 2018. The Argonauts issued a statement in response to Wilder’s comments, stating their expectations of him to fulfill his contractual agreement with the organization. Failure to report to the team in due course will likely result in him being placed on the team’s suspended list for his decision as per his contractual commitments with the organization. By February 27, 2018 the Argos had reportedly offered Wilder a contract extension which would make him one of the highest-paid running backs in the league. On March 3, 2018 the Argos and Wilder agreed to a two-year contract extension, keeping him in Toronto through the 2019 season. The deal is reportedly worth $100,000 per year, with no signing bonus. Wilder played in the first 13 games of the season for the Argos, before suffering a leg injury in Week 16.

Wilder, who began the 2019 season as the Argos’ starting running back, was listed as a healthy-scratch by the Argos during the team’s August 16, 2019 loss to the Eskimos: The loss pushed the Argos record to 1–7. He finished the 2019 season playing in 14 games, rushing 92 times for 464 yards and one touchdown and catching 47 passes for 415 receiving yards and four touchdowns. Prior to entering free agency, Wilder was released upon his request on November 25, 2019.

On January 30, 2020, Wilder signed a one-year contract with the Montreal Alouettes. It was a self-negotiated contract, reportedly for $90,000. In late June 2020, at age 28, due to uncertainty over the 2020 CFL season amid the COVID-19 pandemic, he announced his retirement from playing before being able to play a game with Montreal; he had already received a $25,000 signing bonus from his contract. He accepted a coaching position at his former high school in Tampa, Florida.