This cross-sectional and analytical study aimed to characterize a sample of hypertensive older adults attending a Mobile Health Unit (MHU) in a rural area of central Portugal according to their lifestyle and to analyze the impact of lifestyles on treatment adherence. The sample comprised 235 Portuguese hypertense patients, mainly females (63.8%) with a mean age of 75 years (±8.14 years) and low level of education. The data collection was carried out through a questionnaire consisting of sociodemographic questions, dietary variables, an Alcohol Dependence Questionnaire, an International Physical Activity Questionnaire (Short Version), a Nutrition Health Determination Questionnaire, a Self-Care with Hypertension Scale, and an Adherence to Treatments Measurement Scale. Only 34.5% of the hypertensive patients have controlled blood pressure values (28.2% men and 38% women). However, more than half (56.2%) of the hypertensive patients are classified as adherent to therapeutic measures. The hypertensive individuals, who present higher levels of adherence to the treatment, do not present alcohol dependence, are frequent consumers of aromatic herbs, sporadically consume salt, present good nutritional health, and practice moderate physical activity. The predictor variables for treatment adherence are the self-care dimensions general dietary (p = 0.001), specific dietary (p = 0.034), physical activity (p = 0.031), and antihypertensive medication intake (p < 0.001). Hypertensive patients with healthier lifestyles present better levels of treatment adherence. Therefore, promoting physical activity and healthy dietary practices is necessary to improve treatment adherence and increase antihypertensive treatment’s effectiveness.