KHI will announce its driver lineup in the No. 2 truck for the other 10 CWTS in 2010 at a later date.
Sadler, who drives for Richard Petty Motorsports in the Cup series, will compete in the CWTS season opener at Daytona on Feb. 12. It will mark his first truck race at Daytona and only the fourth time in his career Sadler has competed in a CWTS event.
Sadler's other three starts came in his home state of Virginia. The last one was seven years ago at Martinsville Speedway when he finished 30th after an engine failure.
"Racing in the truck series in 2010 with KHI will be a blast," Sadler said in a news release. "It'll be nice to jump in the truck and go out and race for wins and not have to worry about points.
"Every track that's on my schedule is a place I know we can go out and win. This is going to be a lot of fun."
Harvick, who drives the No. 29 Chevy for Richard Childress Racing in the Cup series, is an experienced truck racer who posted back-to-back wins at the end of the 2009 season in Phoenix and Homestead, Fla.
"I really enjoy being a part of the truck series," Harvick said in the release. "I feel like the combination of Doug George as crew chief and Elliott and I will bring experience and success to the team immediately."
While Harvick was going to victory lane to close out 2009, Ron Hornaday was winning his fourth CWTS title last year and his second while driving the No. 33 truck for KHI.
Terry Blount covers motor sports for ESPN.com.