Direct numerical simulations (DNS) of high hydrogen content (HHC) syngas nonpremixed jet flames have been carried out to study the nitric oxide (NO) formation. The detailed chemistry employed is the GRI 3.0 updated with the influence of the NCN radical chemistry using flamelet generated manifolds (FGM). Preferential diffusion effects have been considered via FGM tabulation and the progress variable transport equation. The results indicate a strong correlation between the flame temperature and NO concentration for pure H2 flame, in which NO formation is characterised by the thermal and NNH mechanisms. The results also indicate a rapid decrease of maximum NO values in the syngas mixtures due to lower temperatures associated with the CO-dilution into H2, thereby increasing the contribution of the prompt-NO mechanism via CH radicals.