Background Self-medication refers to using drugs which have not been prescribed, recommended or controlled by a licensed health care specialist. Marketing, in Chile only admitted for over-the-counter medications, influences the practice of self-medication and extends it to prescription drugs. Thus, a complex self-medication process is started, due to reuse of a previous prescription, using drugs purchased directly at the pharmacy or drugs coming from family first-aid kits. The purpose of this study is to determine the frequency of self-medication, the type of medications involved, the dosages used, and the reasons for this practice. Methods An observation-based cross-sectional study was carried out at three pharmacies belonging to a pharmacy chain in the city of Valdivia (southern Chile). In addition, a previously validated form was used. Customers who requested over-the-counter medications were surveyed to identify the patterns that foster the self-medication practice. Results Of 909 surveyed customers, 75% self-medicate. Of these, 31% stated that they commonly self-medicate due to suffering from light symptoms, such as headaches (19%), the common cold (8.8%), sore muscles (6.7%), and bone pains (5.3%). The group of medications most requested in this study was nonsteroidal anti-inflammatory drugs (NSAIDs) (33%), with diclofenac sodium being the most used (14%). Influence from other people did not exceed 20% and reusing prior prescriptions reached 46%. There were significant differences when assessing consumer knowledge, reading of information leaflets, and opinions about self-medication at each surveyed pharmacy (P < 0.001). Conclusion Most consumers at the surveyed pharmacies use medications without proper knowledge of their benefits, treatment method, and duration. Drug dispensing at community pharmacies should include active pharmacist involvement to divulge the sensible use of drugs.