Abstract Background The benefit of adjuvant therapy for patients with IB gastric cancer (GC) is a topic of debate. This study aimed to evaluate the benefit of adjuvant therapy for patients with IB GC. Methods Overall, the study selected 510 IB GC patients after gastrectomy at the First Medical Center of the Chinese PLA General Hospital, Beijing, China between 2005 and 2018. Overall survival (OS) and disease-free survival (DFS) were analyzed using the Kaplan-Meier method and the log-rank test. Cox regression analyses were used to confirm the independent prognostic factors. Results Patients who received postoperative adjuvant therapy had a longer 5-year OS (92.9 %) than those who received surgery alone (86.7 %; P < 0.05), but the 5-year DFS did not differ significantly between the two groups (92.6 vs. 95.0 %; P > 0.05). Moreover, DFS did not differ between monotherapy, and combination therapy. Uni- and multivariate analyses showed that older age was a significant risk factor for tumor recurrence. Subgroup analyses also failed to identify suitable candidates for chemotherapy. Conclusions Because adjuvant therapy did not demonstrate any benefits in terms of tumor recurrence or DFS, these treatment strategies may be unnecessary for IB GC patients after gastrectomy. Further studies are required to identify subgroups of IB GC patients who may benefit from adjuvant treatments.