Grass pollen allergy has a high prevalence worldwide, making an accurate diagnosis critical in the framework of multifaceted environmental exposures. Our narrative review provides a comprehensive synopsis of component-resolved diagnosis biomarkers for pollen of Pooideae and Chloridoideae grasses, along with practical approaches in European clinical settings. We present a structured overview of allergen components utilized in singleplex, multiparameter, and multiplex IgE immunoassays. Molecular biomarkers have key roles in distinguishing genuine grass pollen sensitization from cross-reactivity and in assessing the risks associated with various IgE sensitization patterns, thereby enabling precise allergy diagnosis and facilitating targeted allergen immunotherapy. Diagnostic algorithms are provided to assist clinicians in making molecular biomarker-based personalized decisions. This tailored approach supports better management of patients with grass pollen sensitizations and allergies.