SUMMARY OBJECTIVE: This online survey aims to compare the side effects that may occur after inactivated severe acute respiratory syndrome coronavirus 2 (COVID-19) vaccination by age groups. METHODS: A total of 411 participants aged 18–100 who received inactivated coronavirus disease 2019 vaccine were included in the study. RESULTS: Participants were divided into four groups according to their ages (i.e., 20–35, 36–50, 51–65, and over 65 years old). Vaccine-related side effects were primarily seen in the 20–35 age group and at least in the >65 age group (p<0.001). The most common side effects were pain, redness, swelling, and numbness at the injection site. Fatigue and headache were other common side effects. After vaccination, 3 (0.73%) participants had hypertension, and 1 (0.24%) had an asthma attack and was admitted to the hospital. No severe side effects were observed in any of the patients. The most critical factors determining the development of side effects were female gender and young age. CONCLUSION: According to the results of this study, different types and rates of side effects are seen in all age groups after the inactivated coronavirus disease 2019 vaccine. Since the 20–35 age group and female gender are at risk of side effects, it would be more appropriate to follow up the side effects after vaccination according to gender and age.