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1. Why animals mate multiple times, owing to the lack of immediate fitness benefits, presents an intriguing problem for evolutionary biologists. Yet, the profusion of this behaviour suggests it must be maintained by natural selection via increased performance. 2. The possible benefits of multiple mating using the leaf beetles Ophraella communa LeSage, the biological control agent of the invasive common ragweed Ambrosia artemisiifolia L., were studied and the fitness consequences of single, twice, three, four, and unrestricted mating events were assessed. 3. Overall, it was observed that the number of copulation events was positively associated with fitness parameters of the insects. Insects performed the best under unrestricted mating regimes, with average increases of 48% in longevity, 75% in fecundity, and 55% in egg hatch rate. In addition, females that experienced unrestricted access to mates maintained very high viability over their entire reproductive lives. Nevertheless, insects also performed better when allowed to mate four times compared with once or twice. 4. The present findings thus support the hypothesis that multiple-mating behaviour is maintained owing to increased fitness benefits in the current and the next generation. Selection for re-mating is, therefore, expected in field populations, which is likely to happen naturally owing to the aggregate lifestyle of O. communa. [ABSTRACT FROM AUTHOR]