Background The Effect of two design constraints, ergonomic and aesthetic, on conceptual design ideation and development was investigated. The chosen constraints were selected as experimental conditions to understand the influence of design constraints more generally on concept design. Methods Workshops were held with participant designers who provided the two constraints (ergonomics and aesthetics). Design outcomes were then assessed by both a sample of potential users and design experts. Results The results indicated that ergonomic, rather than aesthetic, constraints resulted in radically new ideas. Aesthetic outcomes indicated a highly figurative process, resulting in appropriate, yet less novel solutions. Critical function failure was also identified in ergonomic derived outcomes. Conclusions The provision of ergonomic design constraints provided a foundation for the emergence of more novel product design solutions. However, aesthetic derived concepts were assessed as more appropriate in terms of both form and function. The appropriation of ergonomic constraints may provide greater scope for novel design solutions but only if functional expectations are satisfied. Aesthetic design constraints stimulated analogous and metaphoric design approaches. Thus, the results indicate how the provision of differing constraints implicated design outcomes.