The consequences of single versus multiple mating on the longevity, fecundity, and fertility of female emerald ash borers Agrilus planipennis (Fairmaire) were examined. In the first treatment, dissections of the common oviduct showed that 43 of 52 singly-mated females had received spermatophores. In the next two treatments, females were observed to mate one time, then housed either alone (observed separate) or with their mate (observed together). In the fourth treatment, females were paired with a randomly chosen male (unobserved together). Weight (0.0428 ± SE 0.0008 g) and longevity (50.5 ± SE 1.6 d) of female beetles did not differ among treatments. Fecundity, but not fertility, had a significant positive correlation with longevity in all treatments. Almost all of the females ‘Observed together’ laid eggs (87%, N = 31), while significantly fewer females ‘unobserved together’ (61%, N = 31) and ‘Observed separate’ (54%, N = 31) did. The fecundity of females that did lay eggs did not differ among treatments. Based on our results a single mating may be sufficient to ensure maximal fecundity for females, but there is potential for failure of any one mating, and no apparent cost to multiple mating. Thus, multiple mating is likely the best strategy for female emerald ash borers to maximize fecundity. The implications of results for laboratory rearing, and potential population level effects are discussed.