The addition of rituximab to standard chemotherapy has improved the results of the treatment of B cell non-Hodgkin's lymphomas. Under specific circumstances, it can be administered locally, as an alternative to systemic administration. We administered rituximab intrapericardially in an attempt to control pericardial effusion. We report the case of an 85-year-old woman, diagnosed with marginal zone lymphoma, who developed heart failure due to lymphomatous infiltration of the pericardium. We discuss in detail the possibility of intrapericardial treatment of such patients. The patient received rituximab intrapericardially at a dose of 100 mg in addition to systemic rituximab, cyclophosphamide, vincristine and prednisone immunochemotherapy. The treatment proved to be safe and effective. The patient has remained in good health for more than 3 years at the time of writing. Intrapericardial administration of rituximab may be a valuable therapeutic option for patients with lymphoma that involves the pericardium and heart.