"This Old Heart of Mine (Is Weak for You)" is a Holland–Dozier–Holland song that was a hit for American musical group the Isley Brothers in January 1966 during their brief tenure on Motown's Tamla label.

[2] Written by Motown's main songwriting team Holland–Dozier–Holland alongside Sylvia Moy, "This Old Heart of Mine", produced by Brian Holland and Lamont Dozier, was originally intended for The Supremes (who later recorded their own version for their 1966 album The Supremes A' Go-Go).

The single was the group's only major hit while on Motown, whom they left in 1969 to restart their own T-Neck label.

In 1975, English singer Rod Stewart released a remake of this song that charted in several markets.

Record World said that Stewart's version "[remains] faithful to the original, yet [adds] enough rasp and thrust to call it all his own.