Background Neopterin and the kynurenine/tryptophan ratio (KTR) increases with interferon-γ stimulation, indicating Th1-immunity, and thus might be inversely associated with asthma. Objective To examine the association of maternal neopterin and KTR during pregnancy with asthma in the offspring. Methods We analyzed the associations of maternal plasma total neopterin level and KTR in mid-pregnancy with asthma at 7 years among 2,883 children in the Norwegian Mother and Child Cohort Study. Asthma was classified either by registered dispensed asthma medications in the Norwegian Prescription Database or by maternal report. We calculated adjusted relative risks (RR) using log-binomial regression. Results The median (interquartile range) gestational week of blood sampling was 18 weeks (17–19 weeks). The risk of dispensed asthma medications at 7 years was highest among children of mothers in the highest quartile of neopterin level, while the risk was similar in the three lowest quartiles. The adjusted RR (95% CI) of dispensed asthma medications was 1.66 (1.16, 2.38) comparing children of mothers in the highest quartile to those in the three lowest. A similar association was observed for maternal report of asthma at 7 years. When we evaluated allergic versus non-allergic asthma, neopterin tended to be associated with non-allergic asthma. Maternal KTR was not associated with asthma development. Conclusions Our findings indicate that high maternal levels of neopterin, a marker of cellular immune activation, during pregnancy was positively associated with asthma in the offspring. Experimental studies would be needed to further elucidate underlying mechanisms.