A belt positioner 1 for installing a flexible belt into a grooved periphery 12 of a pulley 11. The positioner 1 comprises a belt guiding ramp 2, a pulley flange engaging mechanism 3, a handle 4 and a belt guiding rim 5. The belt guiding ramp 2 is extendible across the grooved periphery 12 and a belt-bearing slanting surface 20 of the ramp 2 enables the belt to be moved into engagement with the grooved periphery 12 when the pulley 11 is rotated about its rotational axis. The pulley flange engaging mechanism 3 comprises a groove 30 extending across the positioner 1 for receiving a pulley flange 13 bordering the grooved periphery 12 and a shoulder 31 bordering the groove 30 for bearing against a side face 14 of the pulley flange 13, wherein the engaging mechanism 3 locks the positioner 1 to the pulley 11 while the belt bears against the slanting surface 20. The handle 4 extends from the ramp 2 and provides a gripping surface 42 for fingers adjacent the ramp 2. In use the handle 4 extends laterally of the grooved periphery 12 and substantially parallel with the rotational axis of the pulley 11. When installing a belt, the positioner 1 need not engage a shaft of the pulley 11 nor be mounted to the pulley 11 in any additional way.