AbstractEthynylphenyl‐methyldichlorosilane (EPDMS) has been prepared as a new monomer for the synthesis of polysilylenes with triple bonds attached to the catenated Si chain. A series of copolymers with methylphenyldichlorosilane (MPDS) as well as the homopolymer, PEPMS, have been synthesized. The content of ethynylphenyl substituents was quantitatively analyzed by FTIR spectroscopy. The optical properties of the new polymers were studied with respect to potential π−σ interaction. No significant bathochromic shift of the UV‐absorption maximum could be detected. Unexpectedly, increasing content of incorporated EPMS units led to a decrease of the (σ−σ*) absorption. The ethynylphenyl‐substituted polysilylenes exhibited strong, temperature‐dependent fluorescence in solution as w