<p>Ladybird beetles, <i>Propylea dissecta</i> and <i>Cheilomenes sexmaculata</i>, are important biocontrol agents, preying on a variety of aphid species. These beetles often coexist and interact, and such interactions may result in reduced female fitness. To assess the impact of conspecific and heterospecific males (<i>P. dissecta</i>) on the reproductive output of <i>C. sexmaculata</i> females, we conducted three experimental treatments: control, conspecific, and heterospecific. Our results indicated that during mating, conspecific males exerted significant interference due to species similarity, disrupting mating attempts of <i>C. sexmaculata</i> females. Following copulation with conspecific males, a reduction in fecundity and egg viability was observed regardless of whether the females were subsequently housed with conspecific or heterospecific males. Multiple mating events occurred in the conspecific treatment, while no heterospecific mating was recorded in the heterospecific treatment. These findings suggest that both conspecific and heterospecific interactions negatively affect the reproductive success of <i>C. sexmaculata</i>, potentially limiting the efficacy of these beetles as biocontrol agents. Further investigation into the mechanisms driving these interspecies interactions is essential to optimise the use of these beetles in integrated pest management strategies.</p>