Lightweight structures become increasingly important to reduce environmental impact and to improve payload/deadweight ratio of ships. Significant weight savings can be accomplished by replacing steel with fiber reinforced polymer (FRP) sandwich panels. An assessment is then necessary to ensure that equivalent fire safety is provided, since the structures are combustible. To support such assessments, this paper presents results from vertically loaded fire resistance tests of two structures: (1) a “conventional” FRP sandwich bulkhead with thermal insulation (providing load carrying fire resistance for 60 minutes) and (2) a multiple core FRP sandwich bulkhead without insulation. Both bulkheads were constructed for and tested with the same design load. The multiple core sandwich bulkhead demonstrated structural fire integrity performance well beyond 60 minutes whilst having a significantly lower structural weight and thickness. The new type of multiple core sandwich structure thus provides great potential, both from a weight-savings and a fire safety perspective.