Abstract We report a large-eddy simulation (LES)/probability density function (PDF) study of a non-premixed CO/H2 temporally-evolving turbulent planar jet flame, which has previously been studied using direct numerical simulations (DNS) with a skeletal chemical mechanism. The flame exhibits strong turbulence–chemistry interactions resulting in local extinction followed by re-ignition. In this study, the filtered velocity field in LES and the PDF transport equations with the interaction-by-exchange with the mean (IEM) mixing model (with molecular transport) are solved by the highly-scalable NGA/HPDF codes with second-order accuracy in space and time. The performance of the hybrid LES/PDF methodology is assessed through detailed a posteriori comparisons with DNS of the same flame. The comparison shows overall good agreement of the temporal evolution of the temperature and mass fractions of major chemical species, as well as the prediction of local extinction and re-ignition. The modeling of multi-scalar mixing is analyzed using the DNS and LES/PDF results. The DNS results exhibit an attracting manifold of the streamlines of the diffusion velocity in composition space, and the LES/PDF results show qualitative agreement on the manifold and joint PDFs of compositions.