Majority of non-Hodgkin lymphoma (NHL) patients who achieve partial response (PR) or stable disease (SD) to CAR T-cell therapy (CART) on day+30 progress and only 30% achieve spontaneous complete response (CR). This study is the first to evaluate the role of consolidative radiotherapy (cRT) for residual FDG activity on day+30 post-CART in NHL. We retrospectively reviewed sixty-one patients with NHL who received CART and achieved PR or SD on day+30. Progression-free survival (PFS), overall survival (OS), and local relapse-free survival (LRFS) were assessed from CART infusion. cRT was defined as comprehensive - treated all FDG-avid sites - or focal. Following day+30 PET scan, 45 patients were observed and 16 received cRT. Fifteen (33%) observed patients achieved spontaneous CR, and 27 (60%) progressed with all relapses involving initial sites of residual FDG activity. Ten (63%) cRT patients achieved CR, and 4 (25%) progressed with no relapses in the irradiated sites. The 2-year LRFS was 100% in the cRT sites and 31% in the observed sites (p.