Optical genome mapping (OGM) is a novel, high-resolution technology for genome-wide detection of structural variants, offering clear advantages over conventional cytogenetics in hematologic malignancies. We applied OGM to a large cohort of patients with acute myeloid leukemia (AML), myelodysplastic syndromes (MDSs), and B-cell acute lymphoblastic leukemia (B-ALL) to evaluate its clinical utility. In AML and MDS, it revealed high-risk alterations such as deletions in 5q31–5q32 and 7q22, and cryptic fusions like NUP98::NSD1 that were missed by karyotyping or FISH. It also identified chromoanagenesis, a catastrophic chromosomal event linked to poor prognosis and often undetectable by standard methods. In B-ALL, OGM uncovered clinically relevant deletions in CDKN2A/B, PAX5, and IKZF1, as well as high-risk ploidy changes like hypodiploidy and hyperdiploidy, all important for risk assessment and frequently underdetected. OGM not only refines diagnosis and improves risk stratification but can also uncover cryptic and complex genomic abnormalities. Our findings support its integration into routine diagnostics to enhance classification, guide treatment decisions, and improve patient outcomes.