Abstract Objective The aim of this study was to examine whether or not cultural differences influence beliefs about the necessity of taking prescribed psychiatric drugs and concern about their adverse effects in psychiatric outpatients in Spain, Argentina, and Venezuela. Methods This cross‐sectional study included 1,372 adult psychiatric outpatients using 2,438 psychotropic drugs and was designed to assess outpatients' beliefs about their prescribed medication. Patients completed sociodemographic, clinical questionnaires, and the Beliefs about Medicines Questionnaire Specific Scale and registered scores ranging from 1 to 5 on each of two subscales: concern and necessity. A “necessity‐concern differential” was obtained by calculating the difference (range −4 to +4). Results The global score, including all drugs in the total sample, had a mean necessity score of 3.50 ± 0.95, a mean concern score of 2.97 ± 0.99, and a mean differential score of 0.54 ± 1.42. The concern and necessity mean scores varied significantly across these three culturally Hispanic countries, probably across drug classes, and were associated with treatment duration. On the other hand, age and education played a very limited role. Conclusions Understanding the diverse effects of culture and society on these attitudes is highly relevant for the development of responsive mental health services in multicultural societies.