Objective To investigate the effect of psychological contract of outpatients with hospital pharmacists on medication adherence, providing reference for improving the management of patients’ medication adherence from the perspective of pharmacist-patient relationship and psychological contract. Methods The 8 patients who received medication dispensing service at the outpatient pharmacies at the First Affiliated Hospital of Zunyi Medical University and the Second Affiliated Hospital of Zunyi Medical University were selected for face-to-face in-depth interviews through a purposive sampling method. In order to get more potential information and adjust flexibly according to the actual situation of the interview, the interviews were set as semi-structured, and the interview content was analyzed by using Colaizzi’s seven-step method of phenomenological analysis and NVivo11.0 software. Results The following four themes about effects of patients’ psychological contract with hospital pharmacists on medication adherence were extracted: from the perspective of patients, the relationship between pharmacists and patients is generally harmonious; pharmacists can basically fulfil their responsibilities; patients’ medication adherence needs to be improved; the status of patients’ psychological contract with hospital pharmacists may affect medication adherence. Conclusion The psychological contract of outpatients with hospital pharmacists has a positive effect on their medication adherence. Effective management on medication adherence should involve the management on patients’ psychological contract with hospital pharmacists.