In semi-crystalline polymer composites, when heterogeneous nucleation occurs with sufficiently high density along the interphase region, the resulting crystal growth is restricted to the lateral direction, so that a columnar layer develops around the fiber, known as transcrystallinity (TC) or transcrystalline layers (TCL). Since Jenckel et al. [Kolloid-Z 129 (1952) 19–24] described TC for the first time in 1952, many researchers have done the investigation of TC to reveal its formation mechanism, aggregate state, and influences on the performance of the materials in the semi-crystalline polymer composites containing various matrixes and fibers under different crystallization conditions. Several aspects of TC in some fiber reinforced semi-crystalline polymer composites were reviewed in the present paper, including the formation and growth mechanisms, factors that affect TC layers, and the influences of TC on the interfaces of fiber/polymer and the properties of composites.