Poly(2-ethyl-2-oxazoline)s (PEtOx) have received substantial attention for various potential biomedical applications, yet they have not been explored as scaffold materials to any extensive degree. A major challenge to open up future applications is to overcome the poor water stability of these materials. We here propose a universal crosslinking strategy for these materials based on a partial acidic hydrolysis of PEtOx to poly[(2-ethyl-2-oxazoline)-co-(ethylenimine)] (PEtOx-EI) followed by exposure to glutaraldehyde vapour to create water-stable scaffolds. To demonstrate the utility of this approach two different fabrication techniques were used to make 2- and 3-dimensional structures, namely solution electrospinning and fused deposition modelling (FDM). Because the partial hydrolysis results in increased hydrophilicity, the crosslinking conditions for the fine PEtOx-EI nanofibers were carefully tuned to enable crosslinking of the nanofibers prior to a loss of the nanofibrous morphology. Conversely, for the thicker FDM printed PEtOx-EI structures the crosslinking conditions are more tolerant. Crosslinking with glutaraldehyde vapour provided water-stability to both 2D and 3D constructs, which is an important asset for biomedical applications.