Harrington was selected in the first round (third overall) of the 2007 MLS SuperDraft by Kansas City Wizards. He finished 3rd overall in voting for Rookie of the Year.
After six years with Kansas City, Harrington was traded to Portland Timbers in December 2012 in exchange for allocation money.[1] He was traded to the Colorado Rapids in exchange for allocation money following the 2014 season.[2]
In January 2016, Harrington signed with the Chicago Fire.[3]