Over the years, concern about the effects of microplastics has grown. Here, we answered the main question “What are the impacts of microplastics on the functional traits of fish species?” through a meta‐analysis. The general impact of microplastic exposure on the functional traits of fishes and specifically on eight variables, namely, behaviour, development, fecundity, feeding, growth, health, hatching and survival was explored. Subgroup analyses were performed to detect correlations between the impact of microplastics and the following factors: species, life stage, habitat, water column habitat, day of exposure to microplastics and microplastic size, type and shape. A meta‐regression analysis allowed understanding the correlation between the impact of microplastics and the size of organisms. Generally, microplastics have a negative effect on the functional traits of fishes. Feeding and behaviour, followed by growth showed the greatest impact. Among the subgroup analysis, four of the eight variables considered showed a significant difference between groups: species, life stage, microplastic shape and days of exposure to microplastics. Depending on their life stage, organisms may be more sensitive to microplastic pollution. Changes in growth rates, development of early life stage and behavioural patterns in fishes may have a negative effect on the structure and functions of aquatic ecosystem in the long term and consequently affect the ability of aquatic ecosystems to provide ecosystem services and sustain human communities. Concern on the effects of microplastics has grown, but “What are the impacts of microplastics on the functional traits of fish species?” Our global meta‐analysis looked at eight functional traits: behaviour, development, fecundity, feeding, growth, hatching, health and survival. Impacts have been investigated depending on species, life stage, habitat, day of exposure and microplastic size, type and shape. Microplastics have a negative effect on fishes' functional traits regardless of size. Feeding, behaviour and growth showed the greatest negative impact. Effects on the structure and functions of aquatic ecosystem may, in the long term, affect the ecosystem services provision.