The 29-year-old striker has been a free agent since leaving the MLS club and will sign for his old SPL club for the rest of the season, subject to a medical.
Chairman Michael Johnston said on Friday night: "Personal terms have been agreed and we don't expect the medical to throw up any problems."
After time with Killie and Rangers, Boyd became the highest scorer in the SPL, racking up 164 goals.
The Scottish international also played for Middlesbrough, Nottingham Forest and Turkish side Eskisehirspor before he moved last year to the United States.
Boyd first joined Kilmarnock in August 2000 and made 153 appearances, scoring 63 goals until he left in January 2006 for Rangers.