Aims: Studying the post-vaccination adverse health events is crucial to determine the confidence and acceptance of the public to the newly-developed COVID-19 vaccines. The present study aimed to investigate the prevalence rates of the adverse health events experienced by the recipients of COVID-19 vaccines in Saudi Arabia. Methodology and results: A cross-sectional study was conducted in October 2021 using a google form of an online self-administered questionnaire sent via different social media platforms for recruiting participants from southwestern Saudi Arabia. The questionnaire was prepared by medical and public health professionals and then translated into Arabic, pilot-studied and validated. Among the 453 Saudi adults who participated in the study with at least one dose of the COVID-19 vaccine, about (77.9%) were males aged 25.5 ± 10.6 years. Most of the participants were college students living in the Makkah region. Nearly 68.3% reported post-vaccination adverse events, such as injection site pain/swelling (91.9%), fatigue (67.9%), bone and muscle pain (65.2%) and flu-like symptoms (58%). The type of vaccine was significantly associated with the development of adverse events p=0.002 (OR of Pfizer-BioNTech versus AstraZeneca: 0.33, 95% CI: 0.18-0.61). Additionally, ageing of more than the 3rd decade, male gender and being married were significantly associated with lower rates of reporting post-vaccination adverse events. Conclusion, significance and impact of study The development of COVID-19 vaccine-related adverse health events had no significant associations with residence, education, occupation, BMI, chronic diseases or smoking. However, age, gender, marital state and vaccine type may be considered significant predictors for developing post-vaccination adverse reactions.