BACKGROUND Frequent disease relapse and a lack of effective therapies result in a very poor outcome in pancreatic ductal adenocarcinoma (PDAC) patients. Thus, identification of prognostic biomarkers and possible therapeutic targets is essential. Besides their function in cell-cell adhesion, desmogleins may play a role in tumour progression and invasion that has not been investigated in PDAC to date. This study evaluated desmoglein expression as a biomarker in PDAC. METHODS Using immunohistochemistry, we examined desmoglein 1 (DSG1), desmoglein 2 (DSG2) and desmoglein 3 (DSG3) expression in the tumour tissue of 165 resected PDAC cases. Expression levels were correlated to the patients' clinicopathological parameters and postoperative survival times. We confirmed these results in two independent gene expression data sets. RESULTS A total of 36% of the tumours showed high DSG3 expression that correlated significantly with shorter patient survival (P=0.011) and poor tumour differentiation (P<0.001), whereas no such association was detected for DSG1 or DSG2. In RNA-Seq data and in microarray expression data, high DSG3 expression correlated significantly with poor survival (P=0.000356 and P=0.00499). CONCLUSIONS We identify DSG3 as a negative prognostic biomarker in resected PDAC, as high DSG3 expression is associated with poor overall survival and poor tumour-specific survival. These findings suggest DSG3 and its downstream signalling pathways as possible therapeutic targets in DSG3-expressing PDAC.