Orbital involvement in chronic lymphocytic leukemia (CLL) is rare with very few published cases. We describe a case of unilateral isolated extraocular muscle enlargement in a patient with CLL. An incisional biopsy was performed from the left medial rectus muscle and histology revealed a lymphocytic infiltrate suggestive of CLL. Complete resolution of signs and symptoms was subsequently achieved with chemotherapy. We would suggest that in patients presenting with atypical clinical features, it is important to consider nonthyroid-related causes of extraocular muscle enlargement and a muscle biopsy should be considered to exclude neoplastic causes.