A 42-year-old woman presented with painless left upper eyelid swelling for one year. Ophthalmologic evaluation revealed left lacrimal gland enlargement, raising suspicion for malignancy. Biopsy confirmed lacrimal gland mucosa-associated lymphoid tissue (MALT) lymphoma. ¹⁸F-FDG PET/CT performed for initial staging demonstrated an additional unexpected hypermetabolic gastric mass. Endoscopic biopsy of the gastric lesion confirmed gastric MALT lymphoma. Although ocular adnexal MALT lymphomas typically present with localized disease and nonspecific clinical manifestations, comprehensive staging may identify additional disease sites. This case highlights the importance of recognizing synchronous involvement by MALT lymphoma at distinct extranodal sites for accurate staging and clinical management.