ABSTRACT Genomic repeat sequences are patterns of nucleic acids that exist in multiple copies throughout the genome. More than 60 Mendelian disorders are caused by the expansion or contraction of these repeats. Various specific methods for determining tandem repeat variations have been developed. However, these methods are highly specific to the genomic region being studied and sometimes require specialized tools. In this study, we have investigated the use of Optical Genome Mapping (OGM) as a diagnostic tool for detecting repeat disorders. We evaluated 19 patients with a prediagnosis of repeat disorders and explained the molecular etiology of 9 of them with OGM (5 patients with Facioscapulohumeral Muscular Dystrophy (FSHD), 2 patients with Friedreich's Ataxia (FA), 1 patient with Fragile X Syndrome (FXS), and 1 patient with Progressive Myoclonic Epilepsy 1A (EPM1A)). We confirmed OGM results with more widely used fragment analysis techniques. This study highlights the utility of OGM as a diagnostic tool for repeat expansion and contraction diseases such as FA, FXS, EPM1A, and FSHD.