An organometallic compound represented by Formula 1: M(L1)n1(L2)n2  Formula 1 wherein M is a transition metal, L1 is a ligand represented by Formula 2-1, L2 is a ligand represented by Formula 2-2, n1 and n2 are each independently 1 or 2, a sum of n1 and n2 is 2 or 3, and L1 and L2 are different from each other: wherein Y1, Y4, X1, X21, ring CY1, ring CY21, ring CY22, ring CY14, A1, a1, a2, b1, c1, R11 to R14, R21 to R23, and Z1 to Z5 are as defined in the specification, * and *′ in Formulae 2-1 and 2-2 each indicates a binding site to M, and * in Formula 3 indicates a binding site to ring CY1 in Formula 2-1.