Background: Although unscheduled readmissions are increasingly being used as a quality indicator, only few readmission studies have focused on surgical patient populations. Methods: An observational study "CURIOS@" was performed at three centers in the Netherlands. Readmitted patients and treating doctors were surveyed to assess the discharge process during index admission and their opinion on predictability and preventability of the readmission. Risk factors associated with predictability and preventability as judged by patients and their doctor were identified. Cohen's kappa was calculated to measure pairwise agreement of considering readmission as predictable/preventable. PRISMA root cause categories were used to qualify the reasons for readmission. Results: In 237 unscheduled surgical readmissions, more patients assessed their readmissions to be likely preventable compared with their treating doctors (28.7% versus 6.8%; kappa, 0.071). This was also reflected in poor consensus about risk factors and root causes of these readmissions. When patients reported that they did not feel ready for discharge or requested their doctor to allow them to stay longer at discharge during index admission, they deemed their readmission more likely predictable and preventable. Doctors focused on measurable factors such as the clinical frailty scale and biomarkers during discharge process. Health-care worker failures were strongly associated with preventable readmissions. Conclusions: There is no consensus between readmitted patients and treating doctors about predictability and preventability of readmissions, nor about associated risk factors and root causes. Patients should be more effectively involved in their discharge process, and the relevance of optimal communication between them should be emphasized to create a safe and efficient discharge process.