Patterns of hepatitis B virus reactivation (HBV‐R) in HBsAg (−)/HBcAb (+) patients with B‐cell non‐Hodgkin lymphoma (NHL) receiving rituximab based immunochemotherapy have not been well described. The retrospective study included 222 HBsAg (−)/HBcAb (+) NHL patients as training cohort and 127 cases as validation cohort. The incidence of HBV‐R in HBsAg (−)/HBcAb (+) B‐cell NHL patients was 6.3% (14/222), of which that in HBsAg (−)/HBsAb (−)/HBeAg (−)/HBeAb (+)/HBcAb (+) population was 23.7% (9/38). Multivariate analysis showed that HBsAg (‐)/HBsAb (−)/HBeAg (−)/HBeAb (+)/HBcAb (+) correlated with a high risk of HBV‐R in B‐cell lymphoma patients (training phase hazard ratio HR, 10.123; 95% confidence interval CI, 3.389–30.239; p < 0.001; validation phase HR, 18.619; 95% CI, 1.684–205.906; p = 0.017; combined HR, 12.264; 95% CI, 4.529–33.207; p < 0.001). In the training cohort, the mortality rate of HBsAg (−)/HBcAb (+) B‐cell NHL caused by HBV‐R was 14.3% (2/14) while that for HBV reactivated HBsAg (‐)/HBsAb (−)/HBeAg (−)/HBeAb (+)/HBcAb (+) population was up to 44.4% (4/9). As a high incidence of HBV‐R and high mortality after HBV‐R was found in HBsAg (−)/HBsAb (−)/HBcAb (+)/HBeAg (−)/HBeAb (+) patients with B‐cell NHL receiving rituximab based immunochemotherapy, prophylactic antiviral therapy is recommended for these patients.