We report a case of hypertrophic olivary degeneration due to cerebellar surgery for a low-grade tumor. A 27-year-old female presented with right-sided paresthesias and intermittent leg paresis following a right cerebellar resection of a tumor 2 weeks prior. One month later, her symptoms remained stable while her neurological examination demonstrated slight right hemi-body hypoesthesia and subtle appendicular ataxia in her right upper extremity. An MRI scan revealed a hypertrophied left anterolateral medulla with increased T2 signal and no diffusion abnormality. The T2 hyperintensity and hypertrophy slowly resolved and she clinically improved without further intervention. Hypertrophic olivary degeneration may be mistaken for tumor progression, post-operative vasculopathy or granulation tissue and should be considered in patients undergoing cerebellar surgery.