Fish growth is one of the most important traits in fish farming and is of great significance to the economic development of aquaculture. By investigating different farmed fish, a large number of studies have shown that growth is mainly affected by environment, genes, and gene-environment interactions; specifically:(1) The environment is the external cause of growth trait regulation, and its impact on growth has generally presented a pattern of dosage effect. Excessive or insufficient amounts of several major environmental factors, such as temperature, light and nutrition, may have adverse effects on the growth of fish. Therefore, seeking optimal conditions becomes the ultimate goal of setting the best aquaculture environment. Additionally, regulating various environmental factors in modern aquaculture possesses significant application potential. (2) Genes are the internal factors that regulate growth traits, and their effects on growth have shown, largely, a relationship of causal effect. Single nucleotide polymorphisms, gene structural variations, ploidy changes, and transgenes of certain genes have shown statistically significant effects on fish growth. Since growth is a complex quantitative trait that is controlled by multiple genes, finding the major genes and then using them in selective breeding becomes an important method for improving growth. The technology of next generation sequencing presents strong advantages in the screening of growth-related candidate genes and in molecular-assisted selection. (3) The influence of gene-environment interactions on growth mainly derives from the different adaptability of genotypes to different environmental conditions, which is characterized by specificity and complexity. Therefore, quantitative research into gene-environment interactions is very limited at present. However, it may be important to consider the gene-environment interactions before developing a program of large-scale commercial breeding. In summary, a full understanding of the impacts of environment, genes, and gene-environment interactions on growth can facilitate better management of fish growth, thereby minimizing cultivation costs and maximizing the ecological benefits.