Abstract: A stackable children's booster chair has a pair of vertical side members spaced apart by a distance W.sub.1. A vertical rabbet had a depth "d", a width W.sub.2 and an upward vertical extent "e" into the lower rear portion of the inner side of each of the vertical side members. A back is located directly above the vertical rabbet and a seat extends between the vertical sides. The back has an upper portion having a thickness that is less than the width W.sub.2 and extends above the side members by a distance slightly less than the vertical extent "e". The back's width W.sub.3 is greater than W.sub.1, but less than (W.sub.1 +2d) so that a vertical rabbet of a second such booster chair is slideable over and engageable with the upper portion of the back when a second such booster chair is placed on top of the first.