This study was performed to evaluate the effects of a patient-centered, tablet computer-based self-monitoring system for chronic disease care. A 3-month randomized controlled pilot trial was conducted to compare the use of a computer-based self-monitoring system in disease self-care (intervention group; n = 33) with a conventional self-monitoring method (control group; n = 30) in patients with type 2 diabetes mellitus and/or hypertension. The system was equipped with a 2-in-1 blood glucose and blood pressure monitor, a reminder feature, and video-based educational materials for the care of the two chronic diseases. The control patients were given only the 2-in-1 monitor for self-monitoring. The outcomes reported here included the glycated hemoglobin (HbA1c) level, fasting blood glucose level, systolic blood pressure, diastolic blood pressure, chronic disease knowledge, and frequency of self-monitoring. The data were collected at baseline and at 1-, 2-, and 3-month follow-up visits. The patients in the intervention group had a significant decrease in mean systolic blood pressure from baseline to 1 month (p < 0.001) and from baseline to 3 months (p = 0.043) compared with the control group. Significant improvements in the mean diastolic blood pressure were seen in the intervention group compared with the control group after 1 month (p < 0.001) and after 2 months (p = 0.028), but the change was not significant after 3 months. No significant differences were observed between the groups in the fasting blood glucose level, the HbA1c level, or chronic disease knowledge. The frequency of self-monitoring of blood glucose level and blood pressure was similar in both groups. The performances of the tablet computer-assisted and conventional disease self-monitoring appear to be useful to support/maintain blood pressure and diabetes control. The beneficial effects of the use of electronic self-care resources and support provided via mobile technologies require further confirmation in longer-term, larger trials.