A 34-year-old woman with breast cancer and the BRCA2: p.Gln3047Ter was treated with olaparib. After tumor progression, cancer genomic profiling testing revealed the BRCA2 p.Gln3047Ter and p.Gln3047Tyr, with 48.9% and 0.37% allele frequency, respectively. These findings shed light on reversion mutation as a resistance mechanism to olaparib in breast cancer.