Cyclic olefin copolymers (COCs) possess excellent properties such as high transparency, high thermal stability, low water absorption, and biocompatibility. The random copolymers of ethylene and norbornene (NB) or its derivatives are commercialized. The physical properties of the copolymers can be improved by the precise control of their molecular structures. The development of single-site catalysts has realized not only the copolymerization of NB with higher α-olefin but also the living copolymerization, which enables us to synthesize a variety of COCs with precisely controlled structures. In this article, we introduce novel NB/olefin copolymers with block, gradient, and star-shaped structures. These copolymers possess excellent optical properties of COC with improved mechanical properties and processability,which will broaden the application fields of COCs.