The objective of this study was to investigate the effects of fats in diets of cattle on methane emissions, and associated impacts on digestibility, milk yield and composition, and rumen fermentation by using meta-analysis. For this purpose, a dataset was constructed compiling data from 29 experiments (27 publications) containing 105 dietary treatments arising from 1339 observations in cattle. Fat supplementation decreased methane production (expressed as g/day, g/kg dry matter (DM) intake, g/kg digestible DM intake, g/kg milk, % of gross energy intake) linearly (P