Invasive species often severely impact ecosystems and human activities in the areas that they invade. Lionfishes (Pterois miles and P. volitans) are regarded as the most successful invasive fishes in marine ecosystems. In the last 40 years, these Indo-Pacific predators have colonised the tropical western Atlantic Ocean, with well-documented detrimental effects on the local fish communities. Around 10 years ago, a second invasion began in the Mediterranean Sea. Given the invasive potential of lionfish and the fact that the ecology and biodiversity of the temperate/sub-tropical Mediterranean offer a different setting from the tropical western Atlantic, specific knowledge on this second invasion is needed. Here, we (i) provide a citizen science-based update on the location of the invasion front in the Mediterranean, (ii) review the scientific knowledge available on the ecology of invasive lionfish, (iii) discuss such knowledge in the context of invasion ecology and (iv) suggest future research avenues on the lionfish invasion in the Mediterranean. While the history and development of the Mediterranean invasion are resolved and some mitigation plans have been implemented locally, the study of the interactions of lionfish with Mediterranean species and their impact on the local biodiversity is in its infancy. Closing this gap will lead to important fundamental insights in invasion ecology and will result in predictions on the impact of lionfish on the ecology and ecosystem services of the Mediterranean. Such information will have practical implications for policy makers aiming to devise sound and efficient mitigation plans.