PURPOSE: This study assesses a novel, automated dose accumulation process during MR-guided online adaptive radiotherapy (MRgART) for prostate cancer, focusing on inter-fractional anatomical changes and discrepancies between delivered and planned doses. METHODS: A retrospective analysis was conducted on seven prostate cancer patients treated with a five-fraction stereotactic body radiation therapy (SBRT), using a 0.35T MRIdian MR-LINAC system. Daily plans were adapted when dose thresholds were exceeded. Planning MRI (pMRI) and daily MRIs (dMRIs) were imported into MIM software for automated and manual dose accumulation procedures. Rigid and deformable image registrations were followed by dose accumulation to compare delivered and planned doses. Manual and automated image registrations were compared by calculating the Hausdorff distance (HD), Jaccard, and DICE metrics. RESULTS: Moderate discrepancies in dosimetric parameters for the planning target volume (PTV) were observed between auto-accumulated and planned doses, such as CONCLUSION: The automated workflow, developed in collaboration with MIM Software Inc., demonstrates high accuracy compared to manual accumulation. The moderate differences observed between planned and accumulated doses emphasize the need for accurate dose accumulation for adaptive plans.