Abstract Objective Previous studies have reported singular factors that may contribute to the photoparoxysmal response (PPR) captured on routine electroencephalography (EEG). This study aimed to investigate the prevalence and multiple clinical characteristics associated with PPR in patients across the lifespan. Methods All adult and pediatric patients who underwent routine EEGs at a tertiary hospital in Australia between January 2019 and December 2020 were studied. Intensive care and prolonged EEGs were excluded. Several potential determinants of PPR were investigated, and their strength of association was analyzed with logistic regression to determine adjusted odds ratios (OR) and 95% confidence intervals (CI). Results In a cohort of 3475 patients, 50 had PPR (1.44%). Significant factors increasing the odds of PPR included sleep deprivation (OR 5.97; 95% CI 2.11–16.89) and generalized epilepsy syndrome (OR 407.21; 95% CI 91.47–1812.85). Patients aged 11–20 (OR 3.77; 95% CI 1.45–9.76) and 21–30 (OR 5.03; 95% CI 1.65–15.32) had increased odds compared with those aged 0–10. Concurrent antiseizure medication during EEG significantly reduced the odds of PPR (OR .33; 95% CI .15–.73). Significance Sleep deprivation, underlying epilepsy syndrome, antiseizure medications, and age significantly impact the occurrence of PPR on routine EEG.