Background: Basal serum tryptase (bST) is the main marker of the mast cell compartment. In spite of the importance of mast cells regarding allergic manifestations, the relationship between bST and allergy-related outcomes has been seldomly described, particularly during early life. In addition, circulating tryptase concentrations depend of mast cell load, genetic determinants, and several physiological, pathological, and exposure factors. This study aimed to assess the potential association between bST and allergy-related outcomes in teenagers from a birth cohort. Methods: This cross-sectional study included 610 teenagers at 15/16 years participating to a French ongoing population-based prospective birth cohort. Participants answered to self-administered questionnaires, received a health check-up and blood sampling. Considered allergy-related outcomes consisted of sensitization by skin prick test and specific IgE measurements, fraction of exhaled NO measurements, and standardized diagnosis of allergy-related morbidities. Results: At 15 years , higher bST was associated with higher prevalence of sensitization to inhalants and foods. Furthermore, bST was positively associated with intermediate-to-high FeNO levels, even after adjustments for covariates including sensitization and eosinophils. After controlling for potential confounders, higher bST was also associated to higher risk of displaying any hypersensitivity reactions, reactions to drugs, and to asthma with associated sensitization. Furthermore, higher bST was associated with poorer control scores among sensitization-associated asthma. Conversely, higher bST was associated with lower risk of presenting dermatitis without associated sensitization. Conclusion: In teenagers from a birth cohort, higher bST was associated with more frequent sensitization, intermediate-to-high FeNO values, and allergy-related morbidities, including asthma.