Axion--Like--Particles are among the most economical and well motivated extensions of the Standard Model. In this talk ALP production from hadronic meson decays are presented. The general description of the hadronization techniques needed in order to calculate ALP emission in mesonic s-- and t--channel tree--level processes is discussed, for pseudoscalar to pesudoscalar mesons. Accordingly, the decay amplitudes for $M_I\to M_F \,a$ are calculated. Finally, bounds on the (low--energy effective Lagrangian) ALP--fermion couplings are derived, from present and future flavor experiments.