Complex formation equilibria of 2-hydroxy-1-naphthoic acid with Cu2+, Ni2+, Co2+ and Mn2+ and the ternary complexes involving Cu2+, 2-hydroxy-1-naphthoic acid and some amino acids containing different functional groups are investigated. Stoichiometry and stability constants for the complexes are estimated at 25 oC and 0.1M ionic strength in 50% dioxane-water mixture. The stability of the complexes follows the trend Cu2+ > Ni2+ > Co2+ > Mn2+, which is in agreement with the Irving–Williams order of the metal ions. Ternary complexes of amino acids are formed by a simultaneous mechanism. The stabilities of ternary complexes are quantitatively compared with their corresponding binary complexes. The concentration distribution diagrams of the complexes were evaluated.