Bemisia tabaci is a major pest of open-field melons in Mediterranean regions. Combining several species of natural enemies can improve pest control but it can give undesirable results when the species engage in antagonistic interactions. This study evaluated the effectiveness of Deraeocoris serenus, Orius laevigatus, and Eretmocerus eremicus as biological control agents and the interactions among the species. This was assessed with the presence–absence of all three species combined in a full-factorial assay. Each microcosm consisted of a melon plant grown in a 5 L pot enclosed in fine mesh, with each of the eight treatments replicated four times. Whiteflies were counted on three leaves per plant, and natural enemies were counted on the whole plants over six weeks. Basal leaves were taken to the laboratory and observed for the emergence of parasitoids. All three natural enemies independently significantly reduced whitefly numbers. Deraeocoris serenus was the most effective biocontrol agent, achieving whitefly reductions of more than 100-fold compared to the control. In contrast, O. laevigatus and E. eremicus achieved reductions of approximately 2.4-fold and 3.6-fold, respectively. No additive or synergistic effects in whitefly control were observed when two or more natural enemies were combined. Deraeocoris serenus and O. laevigatus were found to engage in mutual antagonistic interactions, and these two predators also interfered with the parasitoid. In addition, E. eremicus was also found to interfere with D. serenus. Understanding such interactions is essential for optimizing the management of natural enemies and improving biological pest control.