Objective This study aimed to examine the associations of daytime napping with incident risks of cardiovascular diseases (CVDs) and hypertension (HTN). Methods Data for napping and CVD outcomes in 25 provinces were collected from baseline (2010) and three waves of follow-up (2012–2017) investigations of the China Family Panel Studies. Cox frailty models with random intercepts for the surveyed provinces were used to assess the longitudinal effects of daytime napping on CVD and HTN. Results Compared with non-nappers, 30+ min nappers had higher risks of CVD and HTN, while no significant associations were observed among < 30 min nappers. Incident risks among 30- to < 60-min nappers increased by 22％ [hazard ratio (HR) 1.22, 95％ confidence interval (CI) 1.08–1.39] for CVD and 21％ (1.21, 1.04–1.41) for HTN, respectively, with corresponding HRs of CVD and HTN of 1.27 (1.09–1.47) and 1.38 (1.16–1.65) among ≥ 60 min nappers. Nap-associated CVD risks varied by subgroups, with stronger associations in participants with lower body mass index (< 24 kg/m2), physically inactive persons, smokers, and participants with longer nighttime sleep (≥ 7 h/night). Significant effects of daytime napping were observed on rural and northern residents only, highlighting great regional variations in CVD risks associated with napping habits. Conclusions This cohort study revealed strong evidence that long daytime napping (≥ 30 min) is associated with an increased incidence of cardiovascular events.