Objectives: Using magnetic resonance imaging (MRI), we analysed the clinical manifestations of granulomatous lobular mastitis (GLM) before and after treatment with traditional Chinese medicine (TCM). Methods: This was a retrospective study. Clinical manifestations and imaging features of patients with biopsy-proven GLM before and after treatment were retrospectively analysed from April 2021 to April 2023 at Xiyuan Hospital, China Academy of Chinese Medical Sciences. Results: Among 29 women of childbearing age (mean age, 34.3±3.6 years), Compared to pre-therapy, the number of patients with lumps, ruptures, pain, and menstrual irregularities was significantly reduced (P < 0.05). The Chinese medicine staging demonstrated a transition from bulk to ulcerated (P=0.041). Pre- and post-treatment MRI changes included lesion number, distribution, maximal diameter, time-signal intensity curves (TIC), apparent diffusion coefficients (ADC), and BI-RADS categories 3 and 4a (all P<0.05). Furthermore, substantial changes were seen in chest wall invasion, nipple discharge, increased feeding arteries, and skin edema (all P<0.05). Conclusion: Combining internal and external Traditional Chinese Medicine (TCM) therapy proved successful for GLM. A reliable assessment of therapy efficacy is provided by MRI examination of lesion changes before and after treatment. doi: https://doi.org/10.12669/pjms.40.10.8981 How to cite this: Ning Q, Zhang Z, Ren H, Fan T, Li C. Imaging manifestations and treatment efficacy of Granulomatous Lobular Mastitis: An analysis of 29 cases with internal and external traditional Chinese medicine approaches. Pak J Med Sci. 2024;40(10):2410-2415. doi: https://doi.org/10.12669/pjms.40.10.8981 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.