Abstract Conventional bipolar plates for proton exchange membrane (PEM) fuel cells use extra rubber gaskets to seal the stack, which require an additional curing process at high temperature and increase the manufacturing and assembling time. To reduce the assembling time of fuel cell stacks and achieve gas sealability without using extra gaskets or curing cycles, innovative gasketless carbon composite bipolar plates were developed. To ease the assembling of the cell stacks, special grooves on the edge of the composite bipolar plate are provided for mechanical joining and the behavior of the bipolar plates under the stack compaction pressure conditions was investigated by FE analysis. The mechanical properties of the grooves were measured by the compressive strength test and compared with the FE analysis results. The sealability of the gasketless bipolar plate with grooves was tested to verify the integrity of the design.