An efficient green Heck reaction protocol was performed using a triethanolammonium acetate ionic liquid-palladium(II) catalytic system. The ionic liquid used acts as a reaction medium, base, precatalyst-precursor, and mobile support for the active Pd species. Our experimental investigation indicates that performing the Heck reaction in ionic liquid is superior to the same procedure carried out in triethanolamine. The mechanism of the reaction of triethanolammonium acetate with PdCl(2) was examined using density functional theory (M06 method). It was found that two Pd(II) complexes are formed, one of which acts further as a precatalyst yielding catalytically active Pd(0) complex. The calculated activation energies are in agreement with our experimental findings.