Background: Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease, recently associated with metabolic syndrome, subclinical atherosclerosis and increased risk of cardiovascular disease. Objectives: To investigate the hitherto unknown electrocardiographic (ECG) changes associated with HS, which have recently been associated with significant cardiovascular burden. Methods: Data were obtained from the cross-sectional Danish General Population Study (GESUS). HS diagnosis was based on a validated self-reported questionnaire; 404 individuals met the HS diagnosis criteria and 19 001 controls without HS were identified. Severity of HS was staged according to a modified Hurley score. The ECG parameters of heart rate (HR), PR interval, QRS duration, JTc interval and QTc interval were obtained from 12-lead resting ECGs. We investigated the difference in means by unpaired t-test or anova. Results: HR was significantly higher [mean difference 2·3 beats per min (bpm), 95% confidence interval (CI) 1·2–3·4; P < 0·01] when adjusting for age and sex, but when adjusting for multivariates, there was no significant difference (0·3 bpm, 95% CI –0·7 to 1·4; P = 0·52). Severe HS was significantly associated with increased HR across all models (2·9 bpm, 95% CI 0·7–5·1; P = 0·01). Mean QRS duration was significantly shorter in the group with mild HS but not in the groups with moderate and severe HS. Conclusions: Mean resting HR in patients with severe HS was significantly higher compared with controls. Given that resting HR is associated with increased risk of all-cause and cardiovascular mortality, and that patients with HS have increased risk of cardiovascular events, this finding is potentially important, easily testable and intervenable.