Background The objective of this study was to investigate the changes in blood pressure among patients enrolled in the Telehomecare programme in Ontario, Canada. Methods This observational study utilised a prospective longitudinal cohort design, including patients with heart failure and chronic obstructive pulmonary disease enrolled in the Ontario Telehomecare programme from July 2012 to July 2015. The outcome of interest was change in mean (biweekly) systolic and diastolic blood pressure levels over a six-month period. Patient data were extracted from the Ontario Telemedicine Network database, and analysed using generalised linear mixed model procedures. Results Overall, we analysed data for 3513 patients. Patients were on average 74.1 ± 11.4 years of age; almost half were men, 62% had heart failure, 55% chronic obstructive pulmonary disease and 29% diabetes. At baseline, the mean systolic and diastolic blood pressure levels were 130.4 ± 19.1 mmHg and 72.2 ± 12.5 mmHg for the total sample. At six months, the adjusted reduction in systolic and diastolic blood pressure values were 4.0 mmHg (95% confidence interval: −4.5 to −3.5) and 2.7 mmHg (95% confidence interval: −3.1 to −2.4), respectively. In a subgroup of 1220 patients with uncontrolled blood pressure at baseline (systolic/diastolic blood pressure of 150.7 ± 10.2 mmHg/80.2 ± 13.5 mmHg) the adjusted reduction in systolic blood pressure was 12.5 mmHg (95% confidence interval: −13.4 to −11.6) and in diastolic blood pressure was 7.1 mmHg (95% confidence interval: −7.8 to −6.5) over the six-month period. Conclusions Blood pressure levels were significantly reduced in patients enrolled in the Telehomecare programme, with changes being more pronounced in patients with uncontrolled blood pressure. The sustainability of decreased blood pressure on other clinical outcomes needs further evaluation.