A laser Doppler velocimeter (LDV) for measuring two-dimensional components of velocity vectors based on optical quadrature detection is presented. The LDV uses a simple structure without frequency shifting or multiple wavelengths. In this LDV, the scattered light is monitored in different directions with two detection blocks. In each block, two PDs are used and a 90-deg phase shift is applied to one of the reference beams to detect the absolute value and sign of the beat frequency. We performed an experiment for measuring two-dimensional velocity vectors using a setup introducing orthogonal polarized beams for optical quadrature detection. The experimental results indicate that two-dimensional velocity vectors can be successfully estimated using the proposed method.