The International Linear Collider (ILC) offers a number of unique opportunities for searches for dark matter and dark sector particles. The collider program itself will offer important capabilities, including precision measurements in the scalar sector and direct searches based on the mono-photon signature. With extreme intensities of the high-energy electron and positron beams, the ILC will also enable new fixed-target measurements, both beam dump experiments and dedicated experiments using extracted beams. Described in this contribution are the expectations for these programs, which address all of the possible dark sector portals.