A vehicular drive system is provided with at least one electric motor and a helical gear portion which are accommodated within a casing formed by a plurality of casing members fixed to each other, wherein: said casing includes a first casing member to which a stator of each of said at least one electric motor is fixed, and a second casing member which is fixed to said first casing member so as to cooperate with said first casing member to form a space accommodating said at least one electric motor and which has a support portion supporting said helical gear portion; and a rotor of said each electric motor is rotatably supported at opposite ends thereof by said first casing member and said second casing member, respectively, while said helical gear portion is rotatably supported by said second casing member through said support portion.