PURPOSE: To determine whether morphological changes can occur in the splenic artery (SPA) of autoimmune pancreatitis (AIP) cases, and if present, to compare them with those in pancreatic adenocarcinoma (PAC) to clarify any arterial morphological differences between AIP and PAC. METHODS: A total of 101 AIP cases were included in this study. The presence or absence of morphological change in the SPA was assessed, using arterial phase axial computed tomography images. Subsequently, imaging parameters (imaging pattern, capsule-like rim, other organ involvement, splenic vein [SPV] stenosis, and SPA calcification) were compared between cases with and without morphological changes. Additionally, comparison analyses (visual SPA assessment and % minimal lumen diameter [MLD] stenosis) among normal pancreas, PAC, and AIP groups were performed using early arterial phase (EAP) reconstructed images. RESULTS: In 25 (24.8%) AIP cases, marginal irregularities of the SPA were present. The presence of the capsule-like rim and SPV stenosis were significantly associated with the arterial morphological changes. All cases with morphological changes had a capsule-like rim. Visual assessment using EAP reconstructed images revealed irregularities of the SPA in 9 of 38 AIP cases (23.7%); however, arterial narrowing was not detected in any cases. % MLD stenosis in AIP group was significantly lower than that in PAC group (p < 0.0001). CONCLUSIONS: Although approximately one-quarter of AIP cases potentially demonstrate marginal irregularity in the SPA when it is surrounded by an apparent capsule-like rim, arterial luminal narrowing rarely occurs in contrast to PAC. These arterial findings can help to distinguish AIP from PAC.