Background: Nivolumab has demonstrated a survival benefit for advanced gastric cancer (AGC). However, hyperprogressive disease (HPD) has been reported in various cancers. Methods: The subjects of this retrospective study were AGC patients with measurable disease who received nivolumab, and their tumors were assessed at least 3 times (during prior therapy, before and after nivolumab) in 24 institutions. Tumor growth rates (TGR) during nivolumab were compared to those during prior therapy as reported (Champiat S, 2017). HPD was defined as an increase in TGR > 2-fold. Results: 218 patients were identified as the subjects. While 33 (15.1%) partial response (PR) were achieved, 130 patients (59.6%) showed progression disease (PD), 38 of whom were classified as HPD (17.4%) and 2 patients showed pseudo progression (1.0%). The median progression-free survival (PFS) was 1.9 months (95% CI: 1.9–2.4) and the median overall survival (OS) was 8.5 months (95% CI: 7.1–9.6) in all patients. While patients with PD showed shorter prognosis compared with non-PD patients (median PFS: 1.5 months vs 6.4 months, hazard ratio; 6.0 [95% CI: 4.3–8.4]; p < 0.0001; median OS: 4.7 months vs not reached, hazard ratio; 4.1 [95% CI: 2.8–6.3]; p < 0.0001), there were no differences either in PFS or OS between patients with HPD and those with PD other than HPD (median PFS: 1.5 months vs 1.6 months, hazard ratio; 1.3 [95% CI: 0.9–2.0]; p = 0.1194; median OS: 5.0 months vs 4.6 months, hazard ratio; 1.0 [95% CI: 0.6–1.5]; p = 0.8695). Histological type, liver metastases, carbohydrate antigen 19-9 (CA19-9) level were associated with HPD. Conclusions: HPD was observed 17.4% in AGC patients treated with nivolumab. There were no differences either in PFS or OS between patients with HPD and those with PD other than HPD. Clinicopathological characteristics might be a predict factor for HPD.