Introduction: Fat grafting is a valuable tool for oncologic breast reconstruction, as it enhances aesthetic outcomes. However, concerns regarding oncologic safety and challenges in postoperative imaging have limited the adoption of immediate oncoplastic breast reconstruction (IOBR) with fat grafting. This approach can reduce the need for additional surgeries, shorten recovery time, improve aesthetics, and help mitigate the adverse effects of adjuvant radiation therapy. This study evaluates postoperative, radiological, aesthetic, and patient-reported outcomes of immediate fat grafting in oncoplastic breast reconstruction following lumpectomy. Methods: We conducted a retrospective study of patients undergoing IOBR with immediate fat grafting following lumpectomy (2020–2022). The plastic surgery team performed reconstruction simultaneously with lumpectomy by breast surgeons. Patient satisfaction was assessed using the Breast-Q questionnaire, while expert surgeons evaluated aesthetic outcomes. Lesion characteristics, specimen weight, and postoperative radiation details were recorded. Postoperative breast imaging was reviewed for fat grafting-related abnormalities. Results: Fifteen patients were included, with 87% undergoing postoperative radiotherapy. No major complications or readmissions occurred within 30 days. Breast imaging follow-up showed 91.1% had benign post-surgical changes, while 8.9% required short-term radiologic follow-up. Post-lipoid injection findings appeared in 37.8% of cases, none with calcifications. Patient satisfaction was high (average Breast-Q Score was 74.5), with only one patient requesting additional fat grafting post-radiation. Expert assessments confirmed improved aesthetic outcomes. Conclusion: IOBR with immediate fat grafting is a useful technique for lumpectomy defects across all breast quadrants, demonstrating low complication rates, high patient satisfaction, and positive aesthetic outcomes. Postoperative imaging follow-up revealed no adverse effects related to fat grafting, supporting its potential role as an additional tool in oncoplastic breast reconstruction. Level of Evidence IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.