Rationale and aims Shared decision-making is an approach whereby clinicians and patients make decisions together using the best available evidence. The most common cancers studied in relation to shared decision-making are breast and prostate. However, little is known about shared decision-making in patients with pancreatic cancer. We aimed to identify the determinants that influence pancreatic cancer patients in making treatment decisions during shared decision-making. Methods This qualitative study was carried out at a pancreatic outpatient clinic in an University Medical Center in the Netherlands. We reviewed the literature, observed patients in their option and decision talks, and interviewed healthcare professionals and patients. We used directed content analysis for the literature review, interview and observational data. To categorise the data, we used Bandura’s Social Cognitive theory. Results Related to Bandura’s categories, we identified six subcategories: information provided by healthcare professionals, the patient’s participation role, emotions due to the diagnosis, the relationship between the healthcare professional and the patient, patient characteristics and social support. The important determinants that influenced patients’ treatment decisions were a poor recall of information due to the emotions associated with diagnosis (e.g., completely shaken, fear) and the patient’s participation role preference (mostly collaborative). Most patients preferred to discuss their treatment options and the potential consequences for their daily life with healthcare professionals. In addition, the determinants ‘a well-informed patient’, ‘a trusting relationship between the healthcare professional and the patient’ and ‘time out’ were preconditions for enabling patients to take part in shared decision-making. Patient characteristics and social support had less of an influence on patient’s treatment decisions. Conclusions Better information recall, a trusting relationship with healthcare professionals, and a time out period for the consideration of treatment options are important determinants that influence patients in their treatment decisions and their preferred participation role during shared decision-making.