Underdiagnosed hypertension in the presence of high blood pressure might cause worse conditions due to the absence of appropriate treatment. Nationally representative data of Indonesia show that 64.67% of people with hypertension were underdiagnosed. This study aims to empirically investigate the effect of underdiagnosed hypertension on the risk of cardiovascular diseases including heart attack, coronary heart disease, angina, and other heart problems. A cohort study of respondents aged 40 and older was observed between 2007 and 2014 utilizing longitudinal data from the Indonesian family life survey (IFLS) wave 4 and 5. The analysis was conducted using multivariate logistic regression. Several control variables are involved such as smoking status, obesity, gender, elderly age, working status, and level of education. Of 1,483 people who had hypertension based on blood pressure measurement in the family life survey, only 524 (35.33%) reported they had been diagnosed by medical workers. However, regression analysis shows that people with underdiagnosed hypertension were less likely to suffer cardiovascular problems (odds ratio [OR], 0.58; 95% confidence interval [CI], 0.36-0.92) compared with diagnosed people. This finding might be explained by the information that 21% of diagnosed people had depressive symptoms while the underdiagnosed were less than half of those percentages. A higher number of psychological problems on people who knew they had hypertension was suspected as one of important factors in triggering other chronic diseases. In conclusion, we learn that despite the importance of appropriate medical control and management after hypertension diagnoses, realizing a chronic disease might produce more pressure for someone. It is strongly suggested that the psychological aspect must be taken into account in order to minimize other consequences of hypertension. Encouraging people with hypertension to be more relax could be helpful for them. Additionally, support and warm relationship hopefully come from family and community as the closest part of them.