Wallace acquired his nickname at Lake Hill Speedway when promoter Bob Mueller compared the young, boisterous Wallace to the cartoon character Herman the German. He attended Fox High School in Arnold, Missouri, and has been diagnosed with ADHD. He learned racing by working as a mechanic on his father Russ's race cars — Russ was himself a prolific short-track winner in the Midwest — and on brother Rusty's team, eventually serving as crew chief for Benfield Racing in 1984.
Wallace entered the American Speed Association in 1986, winning Rookie of the Year after finishing 11th with seven top-tens. He ran three ASA full seasons before transitioning to NASCAR. In September 1988, Dale Earnhardt gave Wallace the seat for his first NASCAR Busch Series start at Martinsville, where he finished eleventh. He ran a full Busch schedule in 1989 for brother Rusty's team, winning the Busch Series Rookie of the Year award and finishing sixth in points.
He won his first two career races in 1991 at Volusia County and New Hampshire, finishing second in the Busch championship to Bobby Labonte. That year he also made his Winston Cup debut at North Wilkesboro, and in a race at Charlotte he competed simultaneously against brothers Mike and Rusty — the first time three brothers had raced together in NASCAR since the Flock brothers (Bob, Fonty, and Tim) had done so decades earlier.
Wallace moved to the Cup Series full-time in 1993 driving the No. 40 Dirt Devil Pontiac for SABCO Racing, finishing 23rd in points with three top-tens. After losing his ride, he returned to the Busch Series with FILMAR Racing, winning three times across the 1994 and 1995 seasons at Bristol, Richmond, and Martinsville, and in 1994 made 12 Cup starts as a late-season replacement for the injured Ernie Irvan at Robert Yates Racing.
FILMAR moved to full-time Cup competition in 1996 with Square D sponsorship. Wallace and the team ran through 1998, with his career-best points finish of 22nd coming that year with Andy Petree Racing's No. 55. A consistent if unspectacular Cup performer, one of his most memorable moments came in the 2000 Winston 500 at Talladega, where he finished second behind Dale Earnhardt — Earnhardt's 76th and final career victory. Wallace had pushed Earnhardt to the front in the closing laps.
After leaving Andy Petree Racing, Wallace maintained an active presence in the Busch/Nationwide Series. In 2001 he won at North Carolina Speedway and finished 10th in Busch Series points, also filling in for the injured Steve Park in Cup with notable performances including second at Rockingham. He drove full-time in the Nationwide Series through the mid-2000s with Bill Davis Racing and ppc Racing, regularly finishing in the top ten in points.
He made regular part-time Cup appearances through Michael Waltrip Racing, Furniture Row Racing, and other teams without ever securing a full-time Cup seat again. His most productive late-career Nationwide year was 2011 with RAB Racing, recording eleven top-tens and finishing seventh in points. He achieved what he called the highlight of his racing career in 2012 when he won the DIRTcar Summit Racing Equipment Modified Nationals championship, winning twice and taking seven top-fives. He raced his final NASCAR event in August 2015 at Iowa Speedway with Joe Gibbs Racing, finishing fifteenth.
Post-NASCAR, Wallace continued racing UMP Dirt Modified cars. He finished second overall in the 2016 Charlotte Dirt Track Stadium Super Trucks race and won back-to-back Missouri/Illinois regional championships in 2022 and 2023. In 2025 he won seven races, earned 30 top-fives, claimed his third Missouri/Illinois regional title, and finished fifth in the DIRTcar UMP standings, demonstrating sustained competitiveness well into his sixties.
Wallace co-hosted Speed Channel's NASCAR RaceDay pre-race programme alongside John Roberts from 2005, offering analysis and driver interviews. After his 2015 NASCAR retirement he worked as a reporter for Fox Sports at NASCAR events until 2017 and co-hosted The Late Shift on SiriusXM NASCAR Radio alongside Colton Parayko. Since 2021 he has operated a personal YouTube channel covering motorsport topics, accumulating over 158,000 subscribers by 2026. He co-hosts the Herm & Schrader podcast with Ken Schrader for Dirty Mo Media. In 2023 Wallace was inducted into the Missouri Sports Hall of Fame, joining brother Rusty, who was inducted in 1998.
Kenny Wallace carved a distinctive niche across a 25-year NASCAR career as an entertaining, consistently competitive Busch/Nationwide Series performer whose Cup presence, while never achieving a top-20 points finish, was enriched by memorable moments — most poignantly his role drafting Dale Earnhardt to his final victory at Talladega in 2000. His post-career pivot to dirt racing and media has kept him among the sport's most publicly engaged personalities, and his family connection to Rusty Wallace places him within one of NASCAR's most storied racing dynasties.