A glass fiber-reinforced polyester resin composition including: (A) about 30 to about 80 wt % of two or more kinds of polyester resin; (B) about 20 to about 70 wt % of a vinyl-based copolymer including an acrylic-based graft copolymer, a rubber modified vinyl-based graft copolymer, a copolymer of aromatic vinyl monomers and unsaturated nitrile monomers, or a combination thereof; and (C) about 10 to about 100 parts by weight of glass fiber, based on about 100 parts by weight of the total amount of the polyester resin (A) and the vinyl-based copolymer (B), wherein the polyester resin includes polyethylene terephthalate resin having crystallinity of about 40% or more, is provided.