Olefin cross-metathesis is introduced as a versatile polymer side-chain modification technique. The reaction of a poly(2-oxazoline) featuring terminal double bonds in the side chains with a variety of functional acrylates has been successfully performed in the presence of Hoveyda–Grubbs second-generation catalyst. Self-metathesis, which would lead to polymer–polymer coupling, can be avoided by using an excess of the cross-metathesis partner and a catalyst loading of 5 mol%. The results suggest that bulky acrylates reduce chain–chain coupling due to self-metathesis. Moreover, different functional groups such as alkyl chains, hydroxyl, and allyl acetate groups, as well as an oligomeric poly(ethylene glycol) and a perfluorinated alkyl chain have been grafted with quantitative conversions.