ORMDL proteins are believed to be negative regulators of serine palmitoyl transferase (SPT), which catalyzes the first and rate limiting step in sphingolipid (SL) de novo synthesis. Several single‐nucleotide polymorphisms (SNPs) that are close to the ORMDL3 locus have been reported to increase ORMDL3 expression and to be associated with an elevated risk for early childhood asthma; however, the direct effect of ORMDL3 expression on SPT activity and its link to asthma remains elusive. In this study, we investigated whether ORMDL3 expression is associated with changes in SPT activity and to tal SL levels. Orm d l3‐knockout (Ormd l3^‐/‐) and transgenic (Ormd l3^Tg/wt) micewere generated to study the effect of ORMDL3 on to tal SL levels inplasma and tissues. Cellular SPT activity was measured in mouse embryonic fibroblasts from Ormd l3^‐/‐ mice, as well as in HEK293 cells in which ORMDL3 was overexpressed and silenced. Further more, we analyzed the association of the reported ORMDL3 asthma SNPs with plasma sphingoid bases in a population‐based cohort of 971 individuals. Total C₁₈‐long chain bases were not significantly altered in the plasma and tissues of Ormd l3^‐/‐ mice, whereas C₁₈‐sphinganine showed a small and significant increase inplasma, lung, andliver tissues. Mouseembryonic fibroblast cells from Ormd l3^‐/‐ mice didnot show an altered SPT activity compared with Ormd l3+/2 and Ormd l3^+/+ mice. Overexpression or knock down of ORMDL 3 in HEK 293 cells did not alter SPT activity; however, parallel knock down of all 3 ORMDL iso forms increased enzyme activity significantly. A significant association of the annotated ORMDL3 asthma SNPs with plasma long‐chain sphingoid base levels could not be confirmed. ORMDL3 expression levels seemnot to be directly associatedwith changes in SPT activity. ORMDL3 might influence de novo sphingolipid metabolism downstream of SPT.—Zhakupova, A., Debeuf, N., Krols, M., Toussaint, W., Vanhoutte, L., Alecu, I., Kutalik, Z., Vollenweider, P., Ernst, D., von Eckardstein, A., Lambrecht, B. N., Janssens, S., Hornemann, T. ORMDL3 expression levels have no influence on the activity of serine palmitoyltransferase. FASEB J. 30, 4289–4300 (2016). www.fasebj.org