Although breast-conserving therapy (BCT) is the standard form of treatment for early-stage breast cancer, in patients with small breasts cosmetic results can be poor, especially when the lesion is located on the inner upper quadrant area. This study analyzes our use of autologous free dermal fat grafts (FDFGs) for immediate breast reconstruction. A total of 23 patients who received a partial mastectomy for an inner upper quadrant lesion from 1992 to 2006 at Kagoshima University Hospital were retrospectively divided into three groups according to the reconstructive procedure that was used for the defect after partial mastectomy: immediate reconstruction using an autologous FDFG from the lower abdomen (group FDFG); patients receiving only rotation and fixation of the parenchymal adipose tissue or gland to repair the defect (group GL); and a third group who underwent immediate reconstruction using a miniflap of the latissimus dorsi (group LD). The total duration of surgery in group FDFG was significantly shorter than in group LD (P < 0.01). The mean volume of blood lost in group FDFG was significantly lower than in group LD (P < 0.01). The breast retraction assessment (BRA) of group FDFG was significantly better than for the patients in groups GL and LD (P < 0.01). The total score using the ABNSW system for cosmetic assessment was significantly better in group FDFG than in group GL (P < 0.01). Similarly, the total score in group FDFG using the assessment by the Japanese Breast Cancer Society was significantly higher than that in group GL (P < 0.01). Immediate breast reconstruction for a defect after a partial mastectomy of an upper inner quadrant malignant lesion using FDFG can be especially useful for patients with small breasts.