During establishment and subsequent range expansion, invasive species experience abiotic or biotic factors that are different from those in their native range. As an adaptive response, some of their behavioral, physiological or morphological traits may change to certain degrees. Identifying such changes and underlying mechanisms is critical to invasibility evaluation and risk assessment, and thus informative for the planning of prevention and monitoring means. Invasive ants are among the most widespread and damaging invaders, and some of them have received much research attention in their biology, documented capable of undergoing adaptive changes in their introduced range. Based on the literature over the past 30 years, we summarized such changes by focusing on social structure of colonies, ability to form supercolonies, body size, foraging behavior, interspecific competition, and defense against enemies. Social structure may vary with environments in the division of labor, social form, and between-castes interactions. The ability of forming supercolonies in some invasive ants tends to be higher in introduced regions than in native range. Body size, a key life-history trait influencing invasive ants' biology and their ecological success, has been demonstrated extensively for its plasticity in invasive ants, which could benefit performances of workers. Foraging and competing behaviours have attracted much interest because of their significance for success of ants; they may be flexibly adjusted by ants according to situations of colonies, competitors, resources or other environmental factors. For a few invasive ants, release from enemies is regarded as one of the major reasons for their success outside native range, where the energy originally used for defences would be deployed to growth, reproduction or other aspects of life. Increased tolerance to adverse ambient temperatures, and adaptive shifts in ecological niches under pressures of resource limit, competitors, and climatic factors, have also been reported to some extent. After this, we analyzed the underlying mechanisms of these changes, in the contexts of phenotypic plasticity, adaptive evolution, genetic basis, and symbiotic relationships with microorganisms. We suggest some topics to be addressed in future studies, including associations between social structure and ecological adaptation in little-studied ant invaders; phenotypic plasticity in behavioural syndromes; increased competitive ability after enemy release; and genetic basis for adaptative changes. We also stress the importance of applying knowledge generated in this field to practice, and the need to strengthen international collaborations in researches. This review will hopefully deepen our understanding of ants' invasion mechanisms, and provide clues for the research and management of invasive ants in China, e.g., the red imported fire ant, Solenopsis invicta Buren, and the little fire ant, Wasmannia auropunctata Roger.