PURPOSE: Ultrasonography plays a supplementary role in detecting breast microcalcifications as localizing these microcalcifications without mammographic aid is not always successful. This study aimed to evaluate the clinical implications of intraoperative sonography (IOUSG) in localized excisions after mammographically guided wire insertion. METHODS: Between May 2011 and December 2017, 90 localized excisional biopsies were included. All excisions were preceded by mammographically guided wire insertion. We divided them into two groups according to the use of IOUSG and compared the surgical outcomes between the two groups. RESULTS: Of the 90 localized excisions analyzed, IOUSG was performed in 40 (the USG group) localized excisions and not in the remaining 50 (the no USG group) localized excisions. The median cluster size of the target microcalcifications and the median specimen volume were smaller in the USG group than that in the no USG group (1.4 cm vs. 2.0 cm, p=0.02; 10.9 cm3 vs. 30.3 cm3, p<0.001, respectively). Additional excisions due to the incomplete coverage of the target microcalcifications on the specimen mammography were more frequent in the no USG group than in the USG group (30% vs. 15%, respectively, p<0.001). In the multivariate analyses, performing an IOUSG was the only significant risk factor, reducing the need for additional excision after adjusting the other risk factors (adjusted hazard ratio, 0.203; 95% confidence interval, 0.078–0.529). Performing an IOUSG significantly reduced the specimen volume excised after adjusting the cluster size of the microcalcifications. CONCLUSION: IOUSG could be helpful in improving the accuracy of surgical excision for breast microcalcifications localized with mammographically guided wire insertion.