3D printing of foods is an emerging technology with the potential to develop nutritious and appetising foods to accommodate needs of special consumer groups. For the technology to succeed, studies need to address the composition of printable foods and the stability of printed matrices delivering acceptable sensory properties. This study investigated the effect of gelatine (1–2% w/w), citric acid (0.9–1.5% w/w) and whey protein isolate (WPI) (8–18% w/w) concentration in lemon mousse formulations on printability, physical and sensory properties. The textural properties of the mousses before printing were highly influenced by the concentration of gelatine and WPI but less by citric acid. Gelatine had a gel firming effect, giving a higher firmness and yield stress in mousses, while WPI softened the gel structure. The gel firming effect of gelatine was beneficial to produce 3D-printed mousses with good storage stability after printing, while the addition of WPI gave better-defined layers and a glossier surface of the 3D-printed mousses. The extrusion process disrupted the foam structure, creating a more uniform air bubble distribution, but decreasing the firmness and resilience of the mousses, nevertheless, sensorial attractive and stable 3D-printed mousses were obtained. Increasing WPI concentration in mousses enhanced the shiny appearance, smooth texture and melting mouthfeel. It reduced the rough surface, lumpy and compact texture in mousses, which were associated with the gel firming effect of gelatine. This work shows that protein-enriched 3D-printed lemon mousses with good printability, stability and high consumer acceptance can be produced by formulation design.