Although there is limited evidence for regulating the use of prophylactic antibiotics in reduction mammaplasty, many plastic surgeons prescribe them, even in the postoperative period. This study aimed to conduct a national survey to investigate the antibiotic prophylaxis protocols followed by Brazilian plastic surgeons in reduction mammaplasty. An anonymous survey comprising 19 questions was sent to all 4864 active members of the Brazilian Society of Plastic Surgery (SBCP). The surgeons electronically received the invitation to participate in the survey and the link to fill out the electronic form. In total, 859 surgeons (17.7%) responded. Most respondents (77.8%) were men and aged 35-55 years (61.5%); 58.6% of them had 10-29 years of specialty training. Only a minor proportion of the respondents (0.5%) reported not prescribing antibiotics at any time (95% confidence interval [CI]: 0.0-0.9), 9.9% (95% CI: 7.9-11.9) prescribed them only preoperatively, and 14.6% (95% CI: 12.2-16.9) prescribed continued antibiotic use for 24 h. The majority of the respondents (75.1%; 95% CI: 72.1-77.9) prescribed antibiotics for additional days after discharge. There were significant associations between antibiotic prescription and the surgeons' age group (p = 0.015), time since graduation (p < 0.001), experience in the specialty practice (p = 0.003), SBCP membership (p < 0.001), and surgical site infection rates (p = 0.011). Most responding plastic surgeons affirmed that they prescribed prophylactic antibiotics for more than 24 h in reduction mammaplasty cases. 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 .