To present an orbital extranodal marginal zone B cell lymphoma (MALT lymphoma) with increased choroidal thickness as the first diagnostic sign. Methods: A patient presented with mild blurred vision in the left eye. Progressively increased choroidal thickness was demonstrated by EDI-OCT and ocular ultrasound confirmed diffuse choroidal effusion. Orbital MRI revealed a well-circumscribed intraconal orbital mass surrounding the optic nerve and molding around the globe. An orbital biopsy of the lesion with subsequent histological and immunohistochemical analyses demonstrated MALT lymphoma. Results: After initial treatment with rituximab without improvement, the patient received orbital radiotherapy (36 Gy in 20 sessions). A reduction in choroidal thickness was observed during follow-up visits. Congestion of the choroidal vasculature and choroidal infiltration by the lymphoma are discussed as possible causative mechanisms. Conclusion: EDI-OCT can be a helpful tool to detect the presence of orbital lymphoid tumors in contact with the globe and to monitor response to therapy.