Abstract: An improved shoulder belt guide for use with a child's booster seat positioned on a vehicle seat having a safety belt with a shoulder strap. The guide has first and second generally parallel slots formed in a body member with each slot having a belt access opening for enabling the shoulder strap to be attached to the guide. The guide has a third slot with closed perimeter, and a fourth slot generally parallel to the third slot but having an access opening enable the guide to be adjustably attached to one of a number of loops in a flexible securement strap attached to a booster seat. The strap is attached to the booster seat at several anchor points in order to provide one large loop and a series of small adjustment loops. The large loop portion of the securement strap passes through the third guide slot, while the smaller loops are engaged in the fourth parallel apertured slot so that the position of the guide is determined by which of the several small loops is received in the apertured parallel slot.