Poly(ethylene oxide)‐b‐poly(dimethylsiloxane) (PEO‐b‐PDMS) diblock copolymers have been synthesized by hydrosilation coupling. Allyl‐terminated PEO and dimethylsilane‐terminated PDMS macromers have been prepared by living anionic polymerization, followed by subsequent functionalization. The diblock copolymers, as well as the preformed macromers, have been characterized by gel‐permeation chromatography, vapour pressure osmometry, FTIR spectroscopy and 1H‐, 13C‐ and 29Si‐FTNMR spectroscopy. The results obtained from these techniques are presented in detail for PEO(M̄;n = 2120), PDMS(M̄n = 2220) and the corresponding diblock copolymer.