Experiments of binary and ternary ion exchange equilibrium of heavy metals and sodium were carried out in a complexing iminodiacetic resin Lewatit TP 207. First, binary equilibrium data were obtained at different temperatures and ionic strength and fixed to models considering two different ion exchange stoichiometrics. For ternary equilibrium data, two distinct simple models were applied. One to be applied to systems showing very different selectivity for the metals (for instance, Cu2+/Co2+/Na+) and the other for systems with similar selectivity for the metals (such as Zn2+/Co2+/Na+). The ternary equilibrium data obtained is presented in this work and fitted using the two above mentioned models. These models allow us to obtain the equilibrium parameters for binary and ternary system to be used in the design of equipment using this iminodiacetic resin.