AIMS: Cardiovascular diseases are a global health crisis, with hypertension as a significant risk factor. Traditional cuff-based blood pressure measurements have various limitations, prompting the exploration of photoplethysmography as an alternative for continuous monitoring. This study aimed to assess a cuff-calibrated wrist-worn photoplethysmography-based blood pressure device against European Society of Hypertension recommendations. METHODS AND RESULTS: The study assessed photoplethysmography-based blood pressure measurement stability over 28 days in 150 patients by comparing measurements of the wrist-worn photoplethysmography-based device against three daily automated reference blood pressure measurements. Additionally, awake-asleep blood pressure changes were analysed in 40 patients receiving 24-h ambulatory blood pressure monitoring. Data analysis included overall accuracy and recalibration needs during long-term monitoring, the accuracy of monitoring awake-asleep blood pressure changes, and resilience against hydrostatic pressure changes due to variations in device position. Across 28 days, mean errors of 3.84 mmHg (SD 4.46) for systolic and 4.08 mmHg (SD 3.97) for diastolic blood pressure were achieved. Before recalibration on Day 28, mean errors were 2.49 (SD 3.10) for systolic and 2.98 (SD 3.48) for diastolic blood pressure. Awake-asleep blood pressure change accuracy was demonstrated with mean errors of 2.36 (SD ± 2.40) for systolic and 2.17 (SD ± 2.13) for diastolic blood pressure. Hydrostatic pressure testing indicated resilience against changes in device position. CONCLUSION: The studied wrist-worn photoplethysmography-based device demonstrated accurate and stable blood pressure monitoring over 28 days, during awake-asleep blood pressure changes and hydrostatic pressure changes. These findings support the device's potential for remote patient monitoring. STUDY REGISTRATION: ClinicalTrials.gov identifier: NCT05899959.