Solid pseudopapillary tumor of the pancreas (SPTP) is a class of low-grade malignant tumors that carry a favorable prognosis after surgery. Our group has reported that dysfunctions in the endoplasmic reticulum (ER) protein processing pathway may play a role in tumor development. However, alterations of this pathway in other pancreatic tumors had not been well investigated. In this study, we collected 35 SPTP and pancreatic neuroendocrine tumor (PNET) specimens and described the clinicopathological features of them. We performed immunohistochemistry (IHC) for 6 representative proteins (ERO1Lβ, TRAM1, GRP94, BIP, P4HB, and PDIA4) involved in the ER pathway in both SPTP and PNET specimens. We compared the IHC scoring results of tumors and matched normal pancreas tissues and demonstrated that these proteins were downregulated in SPTP specimens. Five of these proteins (TRAM1, GRP94, BIP, P4HB, and PDIA4) did not display significant changes between PNET and normal pancreas tissue. However, ERO1Lβ was upregulated in PNET tissues compared to the normal tissues, which could be used as a pathological biomarker in the future.