INTRODUCTION: Trust in healthcare and medication, defined as feelings of reassurance and confidence in the healthcare system or medication, may be a key prerequisite before engaging in the use of medication. However, earlier studies have focussed on beliefs about medication rather than trust as predictors of medication adherence. This study therefore aims to simultaneously explore the relationship of trust in healthcare, medication and beliefs about medication, with medication adherence. METHODS: In a cross-sectional study, an online questionnaire was sent out to 1500 members of the Dutch Health Care Consumer Panel of Nivel in November 2018. Respondents were asked to grade their level of trust in healthcare and medication (scale 1-10). The Beliefs About Medicines Questionnaire (BMQ) for general and specific medication beliefs was used to address beliefs, the Medication Adherence Report Scale (MARS-5) to measure medication adherence. Data were analysed using structural equation modelling (SEM) with a backward stepwise approach. Out of 753 people that completed the questionnaire, 407 people used prescription medication and were included in the analyses. RESULTS: A positive association between trust in medication and medication adherence was found (0.044, p < 0.05). BMQ subscales Overuse (-0.083, p < 0.05), Necessity (0.075, p < 0.05) and Concerns (-0.134, p < 0.01) related with medication adherence. BMQ subscale Harm did not relate to medication adherence. CONCLUSION: Trust in medication and beliefs about medication were both individually associated with medication adherence. Healthcare providers should therefore not only focus on patients' medication beliefs, but also on strengthening patients' trust in medication to improve medication adherence.