Adjuvant radiation after breast-conserving surgery remains the standard-of-care treatment for patients with ductal carcinoma in situ and early-stage invasive breast cancer. Multiple alternatives to standard whole-breast irradiation exist including accelerated partial-breast irradiation (APBI). Therefore, the purpose of this APBI guideline is to provide updated data for clinicians as well as recommendations regarding appropriate patient selection and techniques to deliver APBI.Members of the American Brachytherapy Society with expertise in breast cancer and breast brachytherapy in particular created an updated guideline for appropriate patient selection based on an extensive literature search and clinical experience. In addition, data were evaluated with respect to APBI techniques and recommendations presented.Appropriate candidates for APBI include patients aged 45 years or older, all invasive histologies and ductal carcinoma in situ, tumors 3 cm or less, node negative, estrogen receptor positive/negative, no lymphovascular space invasion, and negative margins. With respect to techniques, the strongest evidence is for interstitial brachytherapy and intensity-modulated radiation therapy APBI with moderate evidence to support applicator brachytherapy or three-dimensional conformal radiotherapy APBI. Intraoperative radiation therapy and electronic brachytherapy should not be offered regardless of technique outside of clinical trial.The updated guidelines presented offer clinicians with a summary of data supporting APBI and guidelines for the appropriate and safe utilization of the technique.