Vertical silicon nanowire arrays were fabricated leading to an enhanced photoluminescence (PL) emission and second-order nonlinear optical response. PL from the nanowires was increased by a factor of 50 as compared to bulk silicon. The second order nonlinearity was demonstrated in second-harmonic generation and rotational anisotropic measurements. Enhancement by at least a factor of 80 was achieved as compared to bulk silicon for the p-polarized input and s-polarized output. These enhancements in the silicon characteristics should enable highly desired applications using a silicon platform, such as nonlinear and active devices.