T-cell lymphoblastic lymphoma (T-LBL) is a highly aggressive form of lymphoma with poor clinical outcomes and lacks of a standard treatment regimen. In this study, we assessed the safety and efficacy of tandem autologous hematopoietic stem cell transplantation (auto-HSCT) strategy for adult T-LBL and evaluated prognostic factors affecting survival. 181 Newly-diagnosed adult T-LBL patients were enrolled, 89 patients were treated with chemotherapy alone, 46 patients were allocated to single auto-HSCT group, 46 patients were treated with tandem auto-HSCT. The median follow-up time was 37 months, the 3-year progression/relapse rate of the tandem auto-HSCT group was significantly lower than that of the single auto-HSCT group and chemotherapy group (26.5% vs 53.1% and 54.8%). The 3-year PFS and OS rate of the tandem auto-HSCT group (73.5% and 76.3%) were significantly higher than those of the single auto-HSCT group (46.9% and 58.3%) and the chemotherapy group (45.1% and 57.1%). In the tandem auto-HSCT group, age and disease status after the first transplantation impacted the OS and PFS. Multivariate analysis identified that disease status after the first transplantation was the only independent prognostic factor for patients treated with tandem-HSCT. In addition, diagnostic models of the initial CD8+CD28+/CD8+CD28- T cell ratio in predicting the disease status were found to be significant. Taken together, tandem auto-HSCT can be considered an optimal strategy for adult T-LBL patients (ChiCTR-ONN-16008480).