Objective. Pancreatic cancer is one of the deadliest solid malignancies. Its surgical resection is technically very challenging and has a high risk of complications even after discharge. This study analyzed the risk factors associated with unplanned readmission after pancreatic cancer surgery. Methods. Pancreatic cancer patients who were readmitted within 30 days after surgery were classified as the observation group, while those not readmitted within 30 days postsurgery were classified as the control group. The serum levels of gastrointestinal hormones, stress hormones, and peripheral immune cells of the two groups were compared at different intervals. Results. No significant differences in gender and age were observed between the two groups. At 7, 14, and 21 days postsurgery, the levels of gastrointestinal hormones motilin, gastrin, calcitonin gene-related peptide, and growth hormone-releasing peptide of the observation group were lower than the control group, while the levels of adrenocorticotropin, renin, angiotensin, and plasma aldosterone of the observation group were significantly higher than the control group. In addition, compared to the control group, lower levels of CD4+T cells, CD8+T cells, and NKT cells and higher levels of Treg, Breg, and MDSC cells were observed in the peripheral blood of the observation group. Conclusion. The serum levels of gastrointestinal hormones, stress hormones, and peripheral immune cells could be associated with the risk of unplanned readmission within 30 days after pancreatic cancer surgery.