Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone used to enhance athletic performance and build muscle. Despite being available only with a valid prescription, they are sometimes misused without a physician’s advice. This study assessed the knowledge, attitude, behavior, and positive and negative effects of AAS use among male gym users in Tamil Nadu, India. A cross-sectional survey was conducted among 200 randomly selected gym users using a self-administered questionnaire. The results showed that out of 200 gym users, 76 were AAS users, and 124 were non-users. Most AAS users (73.7%) went to the gym for bodybuilding, while non-users went to maintain health (35.5%) and reduce stress and bodybuilding (32.3%). Around 63% of AAS users experienced side effects such as high blood pressure, mood swings, and pimples, and 53% had gynecomastia. Additionally, almost half of the participants were unaware of the side effects of AAS use. This study highlights the need for creating awareness regarding AAS among gym users. The study concludes that AAS misuse among gym users is prevalent, and users should be educated about the potential risks associated with their use.