Gonadal mosaicism has been reported in a variety of dominant or X-linked conditions and should be considered in all cases of apparent de-novo variation. Recently, some cases of supposed parental germline mosaicism have been shown to result from low-level somatic mosaicism. In most of the cases, mosaicism has been reported for pathogenic single nucleotide variants with only a few cases of copy number variation mosaicism described so far. Herein, we present the first case of parental somatic and gonadal copy number variation mosaicism in the SATB2 gene. We report three brothers presenting with the SATB2-associated syndrome. They all carry the same 121-kb heterozygous intragenic deletion of SATB2. Parental somatic mosaicism was detected by array-comparative genomic hybridization on a maternal blood sample and confirmed by Fluorescence in situ hybridization analysis on blood and buccal cells. This clinical report highlights the importance of investigating for parental somatic mosaicism to estimate the proper recurrence risk for subsequent pregnancy.