The article provides an updated overview of adult-onset hereditary cerebellar ataxias (HCAs), highlighting novel genetic causes and diagnostic approaches. HCAs are rare, progressive neurological disorders with various inheritance patterns, including autosomal dominant (AD), autosomal recessive (AR), X-linked, and mitochondrial. The list of genes associated with adult-onset cerebellar ataxia continues to grow, with recent discoveries including STR expansions in *RFC1* causing CANVAS, *FGF14-GAA* causing SCA27B, and *THAP11*. The genetic basis for SCA4 has also been identified as a STR expansion in *ZFX3*. Given the increasing number of genes and variant types, diagnostic testing can be complex, involving targeted evaluation of STR expansions, next-generation sequencing for conventional variants, and additional tests. The review proposes a diagnostic approach, discusses the challenges with current testing technologies, and explores future advances, particularly the potential of long-read sequencing to transform diagnostic approaches and improve yield. The article emphasizes the need for comprehensive genetic testing, advanced bioinformatics tools, and ongoing gene discovery to narrow the diagnostic gap in HCAs.The article provides an updated overview of adult-onset hereditary cerebellar ataxias (HCAs), highlighting novel genetic causes and diagnostic approaches. HCAs are rare, progressive neurological disorders with various inheritance patterns, including autosomal dominant (AD), autosomal recessive (AR), X-linked, and mitochondrial. The list of genes associated with adult-onset cerebellar ataxia continues to grow, with recent discoveries including STR expansions in *RFC1* causing CANVAS, *FGF14-GAA* causing SCA27B, and *THAP11*. The genetic basis for SCA4 has also been identified as a STR expansion in *ZFX3*. Given the increasing number of genes and variant types, diagnostic testing can be complex, involving targeted evaluation of STR expansions, next-generation sequencing for conventional variants, and additional tests. The review proposes a diagnostic approach, discusses the challenges with current testing technologies, and explores future advances, particularly the potential of long-read sequencing to transform diagnostic approaches and improve yield. The article emphasizes the need for comprehensive genetic testing, advanced bioinformatics tools, and ongoing gene discovery to narrow the diagnostic gap in HCAs.