The present invention relates to an additive for a non-aqueous electrolyte solution including a compound represented by Formula 1 below, a non-aqueous electrolyte solution for a lithium secondary battery including the same, and a lithium secondary battery including the non-aqueous electrolyte solution. NC—(R)n—CN  [Formula 1] (in Formula 1, R is a cycloalkylene group having 3 to 6 carbon atoms in which at least one cyano group (—CN) is substituted or unsubstituted, a haloalkylene group having 2 to 5 carbon atoms in which at least one cyano group (—CN) is substituted or unsubstituted, or an alkylene group having 2 to 5 carbon atoms in which at least one cyano group (—CN) is substituted, and n is an integer of 1 to 5.)