An extender sleeve is provided for elongating and converting the shaft of a conventional golf putter wherein to enable the upper end of the converted putter shaft to be anchored against a portion of the golfer's body, such as the neck or belly, or gripped by one of the golfer's hand's, whereby to improve the swing of the golfer when putting a golf ball. The extender sleeve may be separately attached and removed from the putter shaft as desired or extended and retracted into the shaft for storage when not in use.