A straightforward and highly diastereoselective synthesis of cis-4-hydroxypiperidines is presented. This method allows access to C2 and C4 substituted piperidines, bearing a tetrasubstituted carbon stereocenter at C4. gem-Disubstituted homoallylic amines and ketoaldehydes as carbonyl partners have been rarely used in aza-Prins cyclizations, expanding the scope of this reaction.