We consider a mechanism by which dyons (electrically charged magnetic monopoles) can produce both a T- and P-odd (i.e. time-reversal invariance and parity violating) mixed polarizability (defined by E = -E . B, where E is the energy change when electric (E) and magnetic (B) fields are applied to a system) and a T- and P-odd interaction between two particles: ₁₅ ₁₂₂, where the _i are electron and quark spinors. The latter can create atomic and neutron electric dipole moments. From experimental bounds on these we find limits on the properties of dyons. The contribution of dyons to CP violation in K-meson decays is also estimated.