Macroscopic ‘click’ covalent assembly using azide/alkyne functionalized polymer hydrogels was studied. It is achieved by amplifying chemoselective alkyne-azide click reaction through interfacial multisite interactions. The underlying LEGO-like building process could be generalized with the help of click chemistry. Macroscopic assembly of hydrogels via host–guest chemistry or non-covalent interactions such as electrostatic interactions has been reported. Unlike macroscopic supramolecular assembly, here we report visible ‘click’ covalent assembly of hydrogels at macroscale. PAAm hydrogels modified with alkyne and azide groups, respectively, can click together via formation of covalent bonds. Monomer concentration-dependent assembly and selective covalent assembly have been conducted. Notably, macroscopic gel assembly clearly elucidates the substrate selectivity not observed in the solution reactions of competing monomers.