In this paper, we present the theoretical and experimental results for self-collimation in low-index-contrast photonic crystals (PhCs) in the millimeter-wave (MMW) region of the electromagnetic spectrum. The design of the PhCs is based on their equifrequency contours and the two-dimensional finite-difference time-domain simulation results. In the experiments, the MMW PhCs are fabricated in Rexolite slabs by a CNC micro-milling system. A MMW imaging system is built based on a vector network analyzer. The input source is launched either through a waveguide or a monopole, while the field distribution is acquired by scanning a monopole antenna over the surface of the photonic crystal to detect the profile of the evanescent waves. In both cases, we have observed and characterized the self-collimation effect for both the amplitude and phase of the propagating electromagnetic wave in low-index-contrast photonic crystals.