Background: With the approval of poly(ADP-ribose) polymerase inhibitors(PARPi), US guidelines have expanded the eligibility criteria for germline(g) BRCA1/2 mut testing in order to support treatment decisions. This study assessed real-world BRCA1/2 mut testing rates (any BRCA1/2 mut test, g +/- somatic[s] BRCA1/2 mut test; sB RCA1/2 mut test only; unknown BRCA1/2 mut test) among adult pts with HER2-ABC in the US. Methods: Oncologists abstracted data from medical charts for the next 8-10 consecutive adult pts with HER2-ABC in 2019/2020. Differences in demographics/clinical characteristics among BRCA1/2 mut tested/untested pts were analyzed by t-tests and Fisher’s exact tests. BRCA1/2 mut testing was stratified by hormone receptor (HR) status [HR+/HER2− vs triple-negative breast cancer (TNBC)], practice setting (academic vs community) and type of BRCA1/2 mut test and compared via Fisher’s exact tests. Results: Overall, 407 pts were included; the mean age was 64.2 years, and 99% were female; tumor characteristics: 80% (n=325) HR+/HER2-, 20% (n=82) TNBC. 73% (n=298) of pts received a BRCA1/2 mut test: 47% (n=190) received a g+/- s BRCA1/2 mut test,18% (n=75) received a sBRCA1/2 mut test only and 8% (n=33) received an unknown BRCA1/2 mut test. Compared with BRCA1/2 mut untested pts, BRCA1/2 mut tested pts were younger (62.5 vs 68.9 years; p<0.01), more likely to have a known family history of a BRCA-related cancer (21% vs 8%; p<0.01) and more likely to have TNBC (26% vs 6%; p<0.01). Pts with advanced TNBC were significantly more likely to receive a BRCA1/2 mut test vs pts with HR+/HER2-ABC (93% vs 68%; p<0.01). Pts currently receiving care in an academic setting (n=153) were more likely to receive a g+/- s BRCA1/2 mut test vs pts currently receiving care from a community oncologist (n=254) (58% vs 40%; p<0.01). In contrast, pts currently receiving care from a community oncologist were more likely to receive a sBRCA1/2 mut test only vs pts currently receiving care from a physician at an academic medical center (22% vs 12%; p=0.02). Conclusions: In this study of US adult pts with HER2-ABC, disparities in BRCA1/2 mut testing were observed. Opportunities exist to increase gBRCA1/2 mut testing among pts with HR+/HER2- disease, and among pts treated by a community oncologist. Consistent with guidelines, focused efforts should be developed to educate community oncologists about gBRCA1/2 mut testing.