Congenital disorders of glycosylation are a clinically heterogeneous, rapidly growing group of inherited metabolic disorders. Glycosylation is an enzyme-mediated process by which glycoproteins and glycolipids are formed in cellular compartments, and it is one of the most significant posttranslational modifications of proteins. Congenital disorders of glycosylation are often divided into disorders of N-glycosylation, disorders of O-glycosylation, combined disorders of N- and O-glycosylation, and disorders of biosynthesis of glycolipids and glycophosphatidylinositol anchor. The most numerous and at the same time the most common disorders are disorders of N-glycosylation. The vast majority of glycosylation disorders are inherited in an autosomal recessive manner and present with symptoms affecting multiple organ systems. The most common symptoms are developmental delay, growth retardation, dysmorphic features, neurologic abnormalities, hepatopathy, hypotonia and sometimes recurrent infections. Various methods are used for diagnosis. The main screening methods are isoelectric focusing and capillary electrophoresis of serum transferrin, high-performance liquid chromatography, liquid chromatography combined with mass spectrometry (for N-glycosylation disorders) and isoelectric focusing of serum apolipoprotein CIII (for O-glycosylation disorders). Next generation sequencing, a molecular diagnostic method that has contributed significantly to the discovery of new types of congenital glycosylation disorders, is commonly used to confirm the diagnosis. Early and accurate diagnosis is important to provide adequate patient management and genetic counseling of family members. Treatment is mainly based on symptom relief and prevention of complications. Etiologic treatment is available only for a few types of congenital glycosylation disorders in the form of therapy with monosaccharides or cofactors, and administration of mannose in MPI-CDG has shown the greatest success.