Hamlin raced the full season in the #20 Rockwell Automation Chevrolet in the Busch Series. He finished 5th in the final championship points standings as a rookie in that series. Hamlin also raced in his first Nextel Cup Series races in 2005, making his Cup first start at Kansas Speedway as driver of the #11 FedEx Chevrolet. He made seven starts in the Sprint Cup series in 2005. He finished the Sprint Cup season with three top 10 finishes in seven starts and one pole at Phoenix International Raceway.