INTRODUCTION: Sleep irregularity is increasingly recognized as a modifiable factor for cardiovascular health. This study aims to investigate relationships between short- and long-term sleep irregularity with blood pressure (BP) dynamics among older adults. METHODS: We used data from a prospective cohort involving community-dwelling older adults based on a mobile health (mHealth) app from 2018 to 2022. Short-term exposure was defined as sleep irregularity for one week. Cumulative sleep irregularity, calculated as the area under the curve over 12 months, was regarded as long-term exposure. Outcomes included short-term deviations in BP, longitudinal changes in BP, and cumulative BP over one year. Linear mixed models and generalized additive mixed models were conducted to investigate the associations between sleep irregularity and BP. RESULTS: A total of 1611 participants with a median age of 73.0 years were included. Short-term and long-term cumulative sleep irregularities were associated with increased SBP, DBP, and global BP Z-score. For instance, each SD increment in cumulative sleep onset timing SD was associated with a 0.42 mmHg increase in SBP (95 % CI, 0.25 to 0.60), a 0.31 mmHg increase in DBP (95 % CI, 0.17 to 0.45), respectively. Subgroup analyses indicated stronger associations among males and those with normotension. Strong linear dose-response relationships were further observed between cumulative sleep irregularity and cumulative BP. CONCLUSIONS: Sleep irregularity, in both short-term and long-term exposure, is a risk factor for poor blood pressure control among older adults, highlighting the importance of implementing interventions promoting healthy sleep habits to mitigate cardiovascular risks.