Antigen-escape relapse has emerged as a major challenge for long-term disease control after CD19-directed therapies, to which dual-targeting of CD19 and CD22 has been proposed as a potential solution. From March 2016 through January 2018, we conducted a pilot study in 89 patients who had refractory/relapsed B-cell malignancies, to evaluate the efficacy and safety of sequential infusion of anti-CD19 and anti-CD22, a cocktail of 2 single-specific, third-generation chimeric antigen receptor-engineered (CAR19/22) T cells. Among the 51 patients with acute lymphoblastic leukemia, the minimal residual disease-negative response rate was 96.0% (95% confidence interval [CI], 86.3-99.5). With a median follow-up of 16.7 months (range, 1.3-33.3), the median progression-free survival (PFS) was 13.6 months (95% CI, 6.5 to not reached [NR]), and the median overall survival (OS) was 31.0 months (95% CI, 10.6-NR). Among the 38 patients with non-Hodgkin lymphoma, the overall response rate was 72.2% (95% CI, 54.8-85.8), with a complete response rate of 50.0% (95% CI, 32.9-67.1). With a median follow-up of 14.4 months (range, 0.4-27.4), the median PFS was 9.9 months (95% CI, 3.3-NR), and the median OS was 18.0 months (95% CI, 6.1-NR). Antigen-loss relapse occurred in 1 patient during follow-up. High-grade cytokine release syndrome and neurotoxicity occurred in 22.4% and 1.12% patients, respectively. In all except 1, these effects were reversible. Our results indicated that sequential infusion of CAR19/22 T cell was safe and efficacious and may have reduced the rate of antigen-escape relapse in B-cell malignancies.