Wolbachia interact with their hosts in a broad variety of relationships that range from parasitism to mutualism. To improve the understanding of complex relationships between Wolbachia and host, we performed not only mating and crossing experiments to investigate effects of Wolbachia on mate choice, mating performance, and reproduction in the confused flour beetles Tribolium confusum (Jacquelin du Val), but also quantitative PCR to determine Wolbachia spatiotemporal infection density dynamics within beetles. Wolbachia induced strong cytoplasmic incompatibility, but had no effects on male mate choice and mating performance. Compared with Wolbachia-uninfected females, infected females had very high fecundity irrespective of male's infection status. Wolbachia infection densities in beetles were higher in eggs and adults and in the reproductive tissues and abdomens, whereasWolbachia density in adults did not differ between sexes and among different ages. These results suggest that Wolbachia have evolved mutualistic interactions with T. confusum, which provides the first evidence ofWolbachia mutualisms in this beetle species.We discussed these findings and their evolutionary implications in light ofWolbachia—host interactions.