Purpose: Orbital plasmacytoma is a tumor of plasma cells located in the orbit, which is uncommon and only accounts for less than 1% of total orbital tumors. Sixty-five percent of orbital plasmacytoma are carrying a diagnosis of multiple myeloma. We hereby present two aggressive orbital plasmacytoma cases, a rare orbital malignancy with unsatisfactory outcomes. Methods: This is a series of two orbital plasmacytoma cases. Both initial complaints were unilateral rapid onset of non-axial proptosis with palpable mass in the superior orbit. The first case was IgA-type multiple myeloma with multiple secondary plasmacytomas diagnosed based on systemic evaluation showing hyperproteinemia, IgA level elevation with free κ-light chains, and multiple destructive osteolytic lesions. The second patient unfortunately died before systemic evaluation was carried out. Results: Both patients died less than 2 months after diagnosis, underscoring a very poor prognosis. It is important to perform systemic evaluation and appropriate treatment immediately once the diagnosis has been established. Conclusions: Orbital plasmacytoma is a rare orbital malignancy and is commonly secondary to systemic multiple myeloma. Ophthalmologists should have a high index of suspicion as it has a nonspecific presentation and consider it as one of the differential diagnoses in orbital tumors. © 2022 Authors