AbstractWe report on a 14‐year old boy, his father, and his paternal uncle, all three carriers of a duplication of chromosomal region 11p15.3‐p15.1. The aberration was transmitted by the grandmother, who is carrier of a balanced insertion 46,XX,ins(14;11)(q32.1;p15.3p15.1). In order to determine the precise molecular basis of this structural variant, we performed low‐coverage whole genome sequencing on the boy's father. This approach allowed precise determination of the genomic breakpoints and revealed a duplication of 6.9 Mb, centromeric to the Beckwith–Wiedemann/Silver–Russell syndrome critical region in 11p15.5, that inserted in inverse orientation into 14q32.12 (according to HGVS nomenclature: NC_000014.8:g.92871000_92871001ins[NC_000011.9:g.12250642_19165928inv;T]). To our knowledge, this is the first report of a duplication of 11p15.3‐p15.1 involving more than 40 genes and transmitted through two generations without apparent clinical effects.