We report engineered hydrogel thin-films with varying degrees of covalent crosslinking, which demonstrate enhanced HeLa cell adhesion with decreasing film stiffness. This trend is contrary to previous findings for tumour cell adhesion on hydrogel substrates, and is attributed to the extremely soft nature of the films studied, allowing for a greater cell–film contact area and the development of adhesive focal contacts. Adhesion based on mechanical tuning of the film was decoupled from chemical effects through characterisation and analysis of film surface roughness, hydrophobicity and charge.