He is known for replacing the late Dale Earnhardt after Earnhardt was killed in Daytona in 2001, and for his aggressive driving style.Harvick started racing the way most drivers nowadays do, in carting. For ten years until around 1992, Harvick was highly successful. He raced in NASCAR's AutoZone Elite Division, Southwest Series part-time in 1992 and until 1995, while completing high school. He became a full-time driver in 1995, becoming "Rookie of the Year" in that series that year.

He then moved up to NASCAR's Grand National Division, West Series in 1997, and in 1998 became champion of that series.In 1999, he raced in the NASCAR Craftsman Truck series, and in 2000, joined the NASCAR Busch Series, driving for Richard Childress and winning three times. In 2001 Kevin became the Busch Series Champion while also driving full-time in the Winston Cup Series and finishing in the top 10, a First for any driver. Kevin also was the 2002 IROC Champion in his first try in the series, winning in dominating fashion at the California Speedway and finishing strong in the other 3 events.

For 2001, Childress planned to develop Harvick into Cup with up to seven races in an America Online sponsored third car, number 30, during the 2001 season with plans to run a full schedule in 2002. Those plans changed and Kevin's career was greatly accelerated, albeit under very tragic circumstances. Dale Earnhardt, who had been Childress's flagship driver up to that point, was killed during the final lap of the 2001 Daytona 500. It was rumored that a list of drivers were considered as replacements for Earnhardt such as Earnhardt's son Dale Earnhardt Jr., Canadian CART driver Paul Tracy, and NASCAR driver Jeff Burton, who in mid-2004 eventually joined Richard Childress Racing after being unable to find sponsorship at Roush Racing. In a somewhat controversial move, Childress tabbed Harvick as the replacement. For the first two races afterwards, the cars ran a reverse white and black scheme (what was black became white, and what was white became black), and the pit crew wore generic uniforms, but starting with the third race, they were painted white and red, and Harvick had a white and red uniform, while the pit crew kept the traditional GM Goodwrench Service Plus uniforms, and the number changed from 3 to 29.

On March 11, 2001, Harvick won, in his third Nextel Cup event, by narrowly edging Jeff Gordon at Atlanta Motor Speedway by only six one-thousandths of a second (.006), proving to be one of the closest finishes in NASCAR history since the introduction of electronic scoring in 1993. That finish resulted in one of the classic calls on television, and ironically established the Fox broadcast team's knack for calling thrilling finishes, which seemingly has been a part of their coverage.Harvick would score his second Nextel Cup victory on July 15, 2001 at Chicagoland Speedway in Joliet, Illinois. All in all, he enjoyed one of the most successful campaigns by a rookie in recent memory by scoring 2 victories, 6 top fives and 16 top tens. He also went on to score Rookie of the Year honors while securing a 9th place finish in the 2001 points standings, and score a Busch Series championship.

Ultimately, 2002 was a year of disappointment for Harvick and the entire Richard Childress organization. Harvick was fined for a post race incident with Greg Biffle at Bristol Motor Speedway and would later be suspended for rough driving following a Craftsman Truck race at Martinsville, Virginia. However, Harvick scored his first Nextel Cup pole position at the Daytona International Speedway and scored his third Nextel Cup victory at the Chicagoland Speedway. He finished 21st in the 2002 points standings with 1 victory, 5 top fives and 8 top tens.In 2003, Harvick managed to wage his most successful bid for the championship title, so far. With the addition of crew chief Todd Berrier, Harvick managed to come from 21st in the points standings to 2nd, coming within 234 points of Matt Kenseth by October. In addition, he scored his fourth victory by winning the Brickyard 400 at the famed Indianapolis Motor Speedway. Unfortunately, late season wrecks foiled what could have been a possible championship. Nevertheless, Harvick finished a solid fifth in the standings with 1 victory, 11 top fives and 18 top tens.

However, he also became known for aggressiveness and tough driving. Though he has had his share of run-ins with other drivers, Harvick is not without his sense of humor and charity. This is perhaps best exemplified by his 2004 auctioning of the famous Matt Kenseth T-shirt, which Harvick wore nearly a week after an on-track skirmish with the 2003 Winston Cup Champion at Pocono Raceway. Proceeds from the auction went to Kyle Petty's Victory Junction Gang Camp, a medical camp for children and their families living with chronic and/or life-threatening illnesses.Kevin did not have the year he would have liked in 2004, but is looking forward to the 2005 season after expanding his operations to extra cars. Besides driving for Richard Childress Racing in both the Cup and Busch series, Kevin and his wife, DeLana, have ventured into ownership of their own racing operation, starting their own Busch series team with 2002 Winston Cup Champion Tony Stewart and Tony Raines sharing the driving duties. After a very successful season in the NASCAR Craftsman Truck series in 2004 with the #6 GM Goodwrench Silverado, Kevin has also hired fellow Californian Ron Hornaday to pilot the number 6 GM Goodwrench Chevrolet Silverado for 2005.

Hornaday made his new owner proud in Atlanta once again, as Bobby Labonte was ironically foiled at the finish line of another NASCAR race in Atlanta Motor Speedway in March 18, 2005. Hornaday, in Harvick's truck, defeated Labonte, in the Morgan-Dollar truck, in a two-lap sprint to the finish.On April 3, 2005, Harvick won the Food City 500 at Bristol Motor Speedway despite starting towards the rear of the field. Harvick won without the assistance of crew chief Todd Berrier, who was serving a four-week suspension for having only four gallons of fuel instead of the standard 22 gallons, violating a rule requiring cars qualify with a full load of fuel at the UAW-DaimlerChrysler 400 at Las Vegas Motor Speedway. It was Harvick's fifth win in Nextel Cup competition, Scott Miller's second win as a crew chief, and Richard Childress Racing's 77th victory in Nextel Cup competition.