Imatinib is a tyrosine kinase inhibitor and has rarely been reported to cause pleural effusion. We report the case of an 88-year-old male, known case of gastrointestinal stromal tumor on treatment with imatinib, who presented with a 2-week history of cough and dyspnea. He was diagnosed to have a right-sided pleural effusion and thoracentesis of the fluid revealed an exudate with low adenosine deaminase and negative cytology. Withdrawal of the drug lead to resolution of symptoms. We report this case to highlight the side effect profile of imatinib and warn physicians regarding this potential adverse effect which may be mistaken for metastasis or infection.