Sperm (ejaculate) production is known to be costly to males across diverse taxa. Consequently, depending on mate quality, mated males are predicted to strategically allocate their ejaculate so as to maximize their reproductive success. Such male strategies include sperm competition and the Coolidge effect. Sperm competition is widely explored in a wide range of insect taxa, whereas studies on the Coolidge effect have mainly focused on vertebrates. Nevertheless, the results are often inconsistent with the predictions. In the present study, our aim was to test the hypotheses of sperm competition intensity and Coolidge effect by analyzing the effects of female mating history (in the crab spider Ebrechtella tricuspidata) on male mating behavior. By manipulating mating histories of both females and males, we designed three mating groups: Group A (2 virgin males copulated with 1 virgin female 1 time in sequence), Group B (1 virgin male and 1 previously mated-once male copulated with 1 female 1 time in sequence), and Group C (1 male copulated with 1 female 2 times). We compared the differences in male courtship latency, mating duration, and mating bouts between the first and second mating across the 3 mating groups. The mating latency and mating duration of the second mating were significantly longer than those of the first mating in groups A and B. In contrast, there was no significant difference in mating latency and mating duration between the first and second mating in Group C. Furthermore, there was no significant difference in the mating bouts between the first and second mating across the 3 mating groups. Our results suggest that male E. tricuspidata may be able to detect female mating history and strategically allocate their reproductive investment in terms of mating latency and mating duration. When a male "believed" that the female had mated previously with a rival, this male prolonged his mating duration (reproductive investment). When a male repeatedly mated with the same female, the male did not significantly shorten his mating duration in the second mating relative to the first one, as predicted by the hypothesis of the Coolidge effect. Taken together, our data support the model of sperm competition intensity, but contradict the Coolidge effect. To our knowledge, this is the first study to test sperm competition and the Coolidge effect in spiders.