In this study, the significant operating parameters affecting to the gangue recovery such as froth thickness, pulp density, aeration rate etc. were considered in order to establish a statistical model for the mechanical entrainment, which is one of the significant mechanisms of gangue transportation into froths. To produce the experimental data, laboratory bulk flotation tests were conducted on a copper-iron sulphide ore at the predetermined flotation conditions. Evaluation of the data obtained from the tests showed that the amount of gangue entrained in the froth is a proportion of the water recovered in the concentrate. In addition, some of the water recovery values that have approximately the same magnitudes were obtained from the tests conducted under different flotation conditions. But the gangue recovery values that have different magnitudes were obtained from these tests. In the light of these findings, establishment of a multivariable non-linear estimation model was seen to be a rational approach for description of the relationship between the gangue recovery and other parameters that closely related with the water recovery. It was determined that there is a good agreement between observed results and calculated results from the model developed.