Sensory traps offer some potential as environmentally safe management techniques for control of invasive species. The Eastern mosquitofish (Gambusia holbrooki) is a highly pervasive invasive freshwater fish that competes for food and resources with many native aquatic animals. Invasive mosquitofish may use olfactory cues (pheromones) in communication, and there is potential to exploit these olfactory attractants for control. However, there very little is known of the olfactory receptors used in cue detection, particularly in teleost fish. Through the construction of olfactory transcriptomes, we first identified the olfactory genes of this highly invasive species. We then identified differences in olfactory receptors in male and female fish during breeding through differential gene expression analysis. This project provides information on the olfactory receptor genes present in the eastern mosquitofish revealing genes that may play a role in pheromone cue detection. Taking a genetic approach and assessing the molecular mechanisms driving olfactory driven behaviours has not been widely done. These findings lay the foundation for further research into molecular mechanisms for cue detection in Gambusia holbrooki and invasive fish more broadly.