The present invention relates to a composition for an organic electronic device encapsulant and an encapsulant formed by using the same. A composition for an encapsulant according to an exemplary embodiment of the present invention comprises: 1) a first copolymer comprising the first unit represented by Chemical Formula 1, the second unit represented by Chemical Formula 2, and the third unit represented by Chemical Formula 3; 2) a second copolymer comprising the second unit represented by Chemical Formula 2 and the third unit represented by Chemical Formula 3; 3) one or more photoinitiators; 4) a reactive silicone-based oligomer; and 5) a silicone acrylate-based compound.