Breast cancer (BRCA) is the most frequent malignant disease and cause of death in females. Recent studies have uncovered the crucial roles of necroptosis-related miRNAs in diverse cancers, including BRCA. However, the significance of necroptosis-related miRNA in predicting the prognosis of BRCA remains largely undefined. This study aimed at constructing a miRNA risk signature related to necroptosis and a nomogram for estimating the prognosis of BRCA. The miRNA expression data and related clinical information were downloaded from the BRCA cohort (containing tissue samples from BRCA patients and normal para-cancer patients) of The Cancer Genome Atlas (TCGA) database. We analyzed the miRNA expression profile and screened the differentially expressed necroptosis-related miRNAs between BRCA and non-tumor samples. Then, a risk signature for BRCA patients was developed based on prognostic necroptosis-related miRNAs. The prognostic value of the risk signature was determined by Cox regression analysis. We also constructed a prognostic nomogram based on risk signature and clinicopathological characteristics, and evaluated its clinical potential using a calibration chart. Lastly, to identify potential therapeutic target for BRCA. Six necroptosis-related miRNAs (miR-141-3p, miR-148a-3p, miR-200a-5p, miR-223-3p, miR-425-5p, miR-7-5p) were differentially expressed between normal and BRCA tissues, including five up-regulated miRNAs and one down-regulated miRNA. They were used to construct the risk signature. Receiver Operating Characteristic (ROC) curve analysis indicated that the risk signature had good sensitivity and specificity (2-year area under curve (AUC): 0.627; 3-year AUC: 0.647) and was an independent prognostic factor (univariate Cox regression: hazard ratio (HR) = 1.8066, 95% confidence interval (CI) (1.2867–2.5365), p < 0.05; multivariate Cox regression: HR = 1.5246, 95% CI (1.0830–2.1462), p < 0.05). Calibration chart showed that the nomogram had good accuracy for predicting the prognosis of BRCA patients. We also identified miR-223a-3p as a potential therapeutic target for BRCA. This study identified 6 promising necroptosis-related miRNAs, which were used to construct a signature model to predict BRCA patients’ prognosis. Further, a nomogram based on risk signatures and clinicopathological characteristics was constructed and showed promising potential as an effective and individualized diagnostic tool.