BACKGROUND: Immunization with various vaccines is considered desirable for children with idiopathic nephrotic syndrome (NS) because of their high risk of severe infections. Vaccinations may precipitate relapses of NS, but there is no available data regarding inactivated influenza (flu) virus vaccines. METHODS: We retrospectively reviewed the medical records of children with NS who had received flu vaccines between 2002 and 2015. The day of flu vaccination was defined as day 0, and the period between the pre-vaccination and the post-vaccination days was defined as - X to + Y. The risk ratios and their 95% confidence intervals for NS relapse rate were estimated by generalized estimating equation (GEE) Poisson regression. RESULTS: A total of 104 pediatric patients received 208 flu vaccines. The mean age at onset of NS was at 4.85 ± 3.87 years old. There were 261 NS relapses between days - 180 and + 180. Compared with the relapse rate in the - 180 to 0 interval (1.19 times/person-year), those in 0 to + 30 (1.23), + 31 to + 60 (1.58), + 61 to + 90 (1.41), + 91 to + 120 (1.41), and + 121 to + 180 (1.32) days groups were slightly increased, but without significance. Multivariate analysis using GEE Poisson regression also showed no significant increase in relapse rate in each day group compared with days - 180 to 0. Risk ratios for NS relapse were significantly higher in children who were treated with steroids at the first vaccination. CONCLUSIONS: Our results suggest that flu vaccines should not be avoided in children with NS based on the potential for NS relapses.