Rituximab, a monoclonal antibody directed against the B-cell specific CD20 antigen has been used with success in post-transplant lymphoproliferative disorder (PTLD) of B-cell phenotype. However, the use of such drug in children with liver transplantation and PTLD is very limited. We report a 2-yr-old liver transplant recipient with monomorphic non-Hodgkin lymphoma of B-cell origin. The lymphoma did not respond to immunosuppression withdrawal, with a subsequent allograft rejection. Despite resumption of immunosuppression and rejection treatment, the lymphoma was successfully treated with rituximab.