Provided are a composition, a layer including the composition, a light-emitting device including the composition, and an electronic apparatus including the light-emitting device, wherein the composition includes a first compound and a second compound, the first compound is an organometallic compound represented by Formula 1, the second compound is an organometallic compound represented by Formula 2, the first compound and the second compound are different from each other, |λP(Ir1) - λP(Ir2)| is in a range of 0 nm to about 30 nm, and at least one of Expressions 1 to 4 presented in the specification is satisfied. The substituents in Formulae 1 and 2 and Expressions 1 to 4 are as described in the detailed description.