Polyoxazolines (POx) are increasingly being studied as polymeric building blocks due to the possibility of affording tunable properties. Additionally, as the biocompatibility and stealth behavior of POx are similar to that of poly(ethylene glycol) (PEG), it has become challenging to develop polyoxazoline-based (co)polymers. Even if POx have a lot of advantages, they also show an important drawback, as it has been impossible, to date, to prepare high-molecular-weight polyoxazolines with a low polydispersity index. Thus, it appears important that they be judiciously functionalized. This review covers the multiple ways that polyoxazolines can be functionalized. The use of functional initiators, functional terminating agents, and 2-R-2-oxazolines with an R functional side group is detailed. In conclusion, some perspectives on POx functionalizations are also reported, with functions permitting selective click reactions.