Abstract Rhabdomyosarcoma is a malignant tumor of the skeletal muscles that is occasionally observed in free-living and pet birds. A case of malignant rhabdomyosarcoma in the musculature of the right wing of a captive female cockatiel (Nymphicus hollandicus) was investigated. The clinical aspect and radiographic images suggested an invasive neoplasm. Histologically, the tumor was composed of a patternless array of large primitive polygonal cells or sheets of bizarre cells with giant nuclei and atypical mitoses set in a collagenous stroma. Anaplastic cells were poorly differentiated and exhibited notable cellular and nuclear pleomorphism. Nuclei showed extreme variability in number, size, shape, chromatin distribution and nucleolar size and number. The cross striations were encountered in elongated multinucleated cells known as “strap cells” and in ovoid cells known as “racquet cells” and numerous mitotic figures were also observed. Neoplastic cells were positive for muscle actin and negative for desmin, suggesting the diagnosis of anaplastic rhabdomyosarcoma. It is the first reliable record of a rhabdomyosarcoma in a cockatiel (Nymphicus hollandicus) in Romania.