A compact dual-band bandpass filter (BPF) with high selectivity based on 3D printable groove gap waveguide (GGW) for millimeter application is proposed by the authors. Two stacked dual-mode GGW resonant cavities including TE₁₀₂ and TE₂₀₁ are used to realise a compact structure. The dual-band bandpass response of the GGW BPF is developed from a split-type coupling topology which produced two transmission zeros (TZs) between the two passbands. In addition, two TZs are generated outside the two passbands after introducing a source-load coupling, which achieves a higher frequency selectivity. For verification, a prototype is designed, fabricated and measured. The measured results agree well with the simulated ones, which validates the proposal.