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Abstract Severe cytokine release syndrome (sCRS) and immune effector cell‐associated neurotoxicity syndrome (ICANS) have limited the widespread use of chimeric antigen receptor T (CAR T)‐cell therapy. We designed a novel anti‐CD19 CAR (ssCART‐19) with a small hairpin RNA (shRNA) element to silence the interleukin‐6 (IL‐6) gene, hypothesizing it could reduce sCRS and ICANS by alleviating monocyte activation and proinflammatory cytokine release. In a post hoc analysis of two clinical trials, we compared ssCART‐19 with common CAR T‐cells (cCART‐19) in relapsed/refractory B‐cell acute lymphoblastic leukemia (r/r B‐ALL). Among 87 patients, 47 received ssCART‐19 and 40 received cCART‐19. Grade ≥3 CRS occurred in 14.89% (7/47) of the ssCART‐19 group versus 37.5% (15/40) in the cCART‐19 group (p = 0.036). ICANS occurred in 4.26% (2/47) of the ssCART‐19 group (all grade 1) compared to 15% (2/40) of the cCART‐19 group. Patients in the ssCART‐19 group showed comparable rates of treatment response (calculated with rates of complete remission and incomplete hematological recovery) were 91.49% (43/47) for ssCART‐19 and 85% (34/40) for cCART‐19 (p = 0.999). With a median follow‐up of 21.9 months, cumulative nonrelapse mortality was 10.4% for ssCART‐19 and 13.6% for cCART‐19 (p = 0.33). Median overall survival was 37.17 months for ssCART‐19 and 32.93 months for cCART‐19 (p = 0.40). Median progression‐free survival was 24.17 months for ssCART‐19 and 9.33 months for cCART‐19 (p = 0.23). These data support the safety and efficacy of ssCART‐19 for r/r B‐ALL, suggesting its potential as a promising therapy.