Applications of sandwich panels as 3D shells are limited by the high costs of tooling required for conventional forming operations. This paper presents an investigation into whether incremental sheet forming (ISF) would be mechanically feasible alternative means to form sandwich panels. Process feasibility is assessed through examination of failure modes, thinning and surface quality after application of ISF to various sandwich panel designs. It is shown that ISF can be applied to sandwich panels which have ductile and largely incompressible cores. For a formable sandwich panel, the influence of ISF on the panel and a metal sheet of comparable plastic bending moment were evaluated. Similar trends in tool forces were observed, the sine law had similar accuracy in predicting thinning and the through-thickness deformation was similar for both materials. It is shown that 3D sandwich shells with aluminium foam cores can be produced by using ISF to form a precursor expandable material and that ISF can be used to form impressions on one surface of metal foam core sandwich panels. Failure mode maps are proposed as a future means to represent the boundaries of safe forming regions.