Background <p>Adherence to inhaler therapy is a crucial determinant in the management and control of asthma. However, real-world evidence indicates that only 30–70% of patients adhere to prescribed treatments. This study aimed to identify the psychological and behavioral factors influencing inhaler adherence among patients with asthma.</p> Methods <p>This cross-sectional study was conducted on 300 patients with a confirmed diagnosis of asthma based on GINA criteria at Imam Khomeini Hospital, Ardabil, Iran, during the winter of 2021–2022. Participants were selected through a census sampling method. Data were collected using a researcher-developed questionnaire and analyzed statistically.</p> Results <p>Inhaler adherence was positively associated with patient knowledge, disease acceptance, treatment acceptance, self-efficacy, and perceived benefits of inhaler use. Conversely, fear of side effects and inhaler-related stigma were negatively associated with adherence (<i>P</i> &lt; 0.05). Significant differences in adherence-related variables (knowledge, disease and treatment acceptance, stigma, self-efficacy, and perceived benefits) were found across different educational levels and between urban and rural patients (<i>P</i> &lt; 0.05).</p> Conclusions <p>Psychological and behavioral factors play a significant role in adherence to inhaler therapy in asthma patients. Regular assessment of patients’ knowledge, beliefs, and behavioral patterns regarding inhaler use during clinical visits may enhance self-management and improve treatment outcomes.</p>