A mold for manufacturing interlocking, dry-cast concrete retaining wall blocks in an upright orientation comprises a mold box comprising two side walls joined to end walls to define a mold cavity, a top face, and a substantially open bottom face. Partitions configured to define a space between adjacent blocks or a space between a block and a side of the mold box extend parallel to the side walls of the mold box substantially from the top face into the mold cavity, to form first transverse portions of the profile of the top and bottom surfaces the blocks which do not include any undercut portion that would impede removal of the mold box in a substantially vertical direction. At least one removable insert comprises insert members which, when positioned in the mold box beneath the partitions, form remaining transverse portions of the profile of the top and bottom surfaces, the remaining transverse portions including at least one undercut portion. The insert members, when in position in the mold box for casting, are substantially in lateral alignment with respective bottom surfaces of at least some of the partitions and can be inserted and retracted through openings in an end wall of the mold box.