Background Lymphoma of the lacrimal sac is rare, often misdiagnosed clinically. This study aimed to investigate the imaging features of these tumors and provide suggestions to aid the diagnosis. Methods In this retrospective study, five cases were assessed according to magnetic resonance imaging (MRI), computed tomography (CT), and pathological findings. All five patients underwent MRI and contrast-enhanced T1-weighted imaging (CE-T1WI), of which four patients underwent dynamic contrast-enhanced (DCE) MRI and three patients underwent CT. Results Four cases and one case had a lymphoma in left and right medial canthus, respectively. Soft tissue surrounding the eyelids, subcutaneous tissue in the nasal dorsum, and involvement of the entire nasolacrimal canal were demonstrated in all five lesions. In two cases, the mass invaded the extraconal space. In one case, the mass invaded the adjacent medial rectus muscle and nasal area. Well-defined margins were observed in three cases and ill-defined margins in two cases. All cases showed homogeneous isointense lesions on T1WI. Four cases showed homogeneous isointensity and one case demonstrated heterogeneous isointensity on T2WI. After contrast injection, the lesion showed slight homogeneous isointensity and moderate enhancement in four cases and heterogeneous isointensity and moderate enhancement in one case. In the four patients who underwent DCE-MRI, a plateau pattern was revealed in three cases and washout pattern in one case. In the three cases who underwent CT, two cases had isointense and one case had hyperintense lesions. The lacrimal duct was remodeled and the surrounding bone compressed. Conclusions Tumors of the lacrimal sac showed homogeneous and isointense patterns on T1WI and T2WI with mild-to-moderate enhancement and a plateau pattern on DCE-MRI. CT showed remodeling of the lacrimal duct with bone compression.