Background: Resistant hypertension (RH) consists of increased blood pressure (BP) despite the use of 3 or more antihypertensives or BP control only when is use of 4 or more antihypertensives. It is fundamental to exclude pseudoresistance, which can be attributed to poor therapeutic adherence. Adherence evaluation, generally by the Morisky-Grenn test, is important because, when appropriate, it is associated with fewer cardiovascular complications and better BP control. Objectives: To evaluate the adherence of patients with RH and to investigate its relation with epidemiological, anthropometric and clinical characteristics, as well as to estimate the prevalence of pseudoresistance and to outline strategies to improve adherence. Methods: Retrospective observational cohort from an interview with patients followed at an outpatient clinic for RH. Therapeutic adherence, demographic, anthropometric data, cardiovascular risk factors, comorbidities, complementary exams and BP level were collected. One-way ANOVA and Student's t-tests were used for normal variables, and the Kruskal-Wallis and Mann-Whitney tests were used for non-normal tests. Categorical variables were compared using the Chi-Square test. We considered a 5% significance level in all tests. Results: 217 individuals were included. Of these, 17% had poor adherence. Epidemiological and clinical characteristics, complications, comorbidities, BP level or drugs used were statistically insignificant between groups. The poor adherence group used significantly more drugs (p = 0.0313) and 28% of pseudoresistance was estimated. Conclusions: Most of the individuals presented good therapeutic adherence by the Morisky test. Only the number of antihypertensive drugs had a statistically significant influence on adherence, while the epidemiological, anthropometric and clinical characteristics were statistically insignificant.