Diffuse large B-cell lymphoma is the most common histologic subtype of non-Hodgkin lymphoma. Secondary involvement of the heart is seen late in advanced cases, it is uncommon for diffuse large B-cell lymphoma to present as intracardiac mass. A 26-year-old female patient presented with progressive shortness of breath, facial swelling, and lower limb edema. Imaging investigations by echocardiography and computed tomography showed a large right atrial mass that was obstructing the tricuspid valve. Open biopsy was taken, histopathology showed diffuse large B-cell lymphoma. She received six cycles R-CHOP chemotherapy (rituximab, cyclophosphamide, epirubicin, vincristine, and prednisone) with complete resolution of the mass. Diffuse large B-cell lymphoma can present with atypical and uncommon sites such as the heart as the first presentation. Early diagnosis and appropriate management is crucial given the poor outcome with late presentation. A high index of suspicion and the proper investigations is recommended to allow for early intervention and favorable outcomes as what happened with the case under discussion.