Brain tumor segmentation in Magnetic Resonance Imaging (MRI) is crucial for accurate diagnosis and treatment planning in neuro-oncology. This paper introduces a novel multi-parallel blocks UNet (MPB-UNet) architecture for automated brain tumor segmentation. Our approach enhances the standard UNet model by incorporating multiple parallel processing paths, inspired by the human visual system’s multi-scale processing capabilities. We integrate Atrous Spatial Pyramid Pooling (ASPP) to effectively capture multi-scale contextual information. We evaluated our proposed architecture using the publicly available Low-Grade Glioma (LGG) Segmentation Dataset. This comprehensive collection comprises 3929 axial slices of FLAIR MRI sequences from 110 patients, each slice paired with a corresponding segmentation mask. Our model demonstrated superior performances on this dataset compared with existing state-of-the-art methods, highlighting its effectiveness in accurate tumor delineation. We provide a comprehensive analysis of the model’s performance, including visual results and comparisons with other architectures. This work contributes to advancing automated brain tumor segmentation techniques, potentially improving diagnostic accuracy and efficiency in clinical settings. The proposed multi-parallel blocks UNet shows promise for integration into clinical workflows and opens avenues for future studies in medical image analysis. Our model achieves strong performances across multiple metrics: 99.86% accuracy, 99.86% precision, 99.86% sensitivity, 99.86% specificity, 99.80% Dice Similarity Coefficient (DSC), and 92.17% Average Intersection over Union (IoU).