In applications to turbulent reactive flows, the probability density function approach requires a model for molecular diffusivity. The objective of the present work is to develop a consistent model for passive scalars in turbulent flows, improving the calculation of the velocity‐scalar correlation coefficient. This is done by using the Langevin model for the velocity and by adjusting two model parameters of a velocity‐biased mixing model for the scalar, which are determined by reference to homogeneous isotropic turbulent flows with a uniform mean cross‐stream scalar gradient. Calculated and measured profiles are in good agreement.