Most flowering plants engage animals to carry out the essential service of pollination. The majority of these plants have evolved flowers that advertise rewards for this service via visual and chemical cues such as petals and scent. There are however a number of species whose false advertisements draw pollinators to rewardless flowers. Among them are the sexually deceptive orchids, which employ a precise chemical mimicry of female wasp sex pheromones to attract male wasps for pollination. This study utilizes neutral genetic markers to examine the consequences of sexual deception for mating patterns in two sympatric Australian orchids. We show through behavioural and population genetic analysis that the chemical mimicry crucial to sexual deception is also responsible for pre-pollination reproductive isolation and potentially even speciation. We also report paternity and mating system analyses that demonstrate that sexual deception results in near exclusive outcrossing despite clonality as well as multiple paternity–a rarity for orchids. We show that this pollination strategy is an adaptive solution to the problem flowers face of simultaneously attracting pollinators and persuading them to leave quickly.