 A laser-induced transient grating technique with femtosecond temporal resolution was used to study the anisotropy and hot carrier diffusion coefficient in monocrystalline diamond, revealing that the ambipolar diffusion coefficient is an isotropic between 100 and 110 crystallographic directions. The carrier energy distribution can be controlled on a subpikre second timescale by an additional laser pulse with photon energy below the width of a diamond band gap absorbed by the excited carrier system, and Monte Carlo simulations confirm the presence of a hot carrier diffusion regime in diamond. This article was authored by Martin Kozak, Franti Ektrogenic, and Petta Malli.