Disclosed are compositions and methods for targeted treatment of CD99-expressing cancers. In particular, chimeric antigen receptor (CAR) polypeptides are disclosed that can be used with adoptive cell transfer to target and kill CD99-expressing cancers. Also disclosed are immune effector cells, such as T cells or Natural Killer (NK) cells, that are engineered to express these CARs. Therefore, also disclosed are methods of providing an anti-tumor immunity in a subject with a CD99-expressing cancer that involves adoptive transfer of the disclosed immune effector cells engineered to express the disclosed CARs. Also disclosed are multivalent antibodies are disclosed that are able to engage T-cells to destroy CD99-expressing malignant cells.