To describe clinical and imaging features and surgical treatment of equine mandibular aneurysmal bone cysts (ABCs) with β-tricalcium phosphate (TCP). 3 horses (cases 1, 2, and 3) and 1 pony (case 4) with histologically confirmed ABC. All cases had mandibular swelling with intact adjacent skin. Cases 1 to 3 had a body condition score of 3/5 and case 4 had 2/5 and showed quidding during mastication and, at oral examination, large interdental spaces and loose elements adjacent to the swelling. Radiography or CT was performed in all cases. In cases 1, 3, and 4, an expansile septate cystic space-occupying lesion with mass effect on the adjacent cortices and teeth was seen without compact bone destruction. Case 2 showed a heterogeneous osteolytic mass with multifocal cortical lysis and interruption. Case 4 had severe dental abnormalities of deciduous and precursors of permanent teeth. ABCs were surgically treated and filled with only TCP (case 3) or in combination with autologous bone marrow (cases 1, 2, and 4). Cases 1 through 3 showed an uneventful reduction in ABC size with increased opacity/attenuation. In case 4, a surgical site infection occurred. After removal of TCP remnants, the ABC healed satisfactorily, but remaining dental abnormalities necessitated dietary adjustments to maintain an acceptable body condition score. Treatment of ABCs with TCP had a favorable outcome and good long-term prognosis. In young specimens, the expansile effect on the development and eruption of neighboring teeth can influence and determine final functionality of the diseased dental quadrant.