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Abstract A class of multi‐band bandpass filters (BPFs) based on glass‐integrated multi‐resonant cells (MRCs) are reported. Each MRC comprises multiple in‐parallel connected series‐type resonators that create passbands in‐between transmission zeros (TZs)—located at the resonators’ resonance. The MRCs can be combined in multi‐stage configurations to create high‐order multi‐band transfer functions or used in the RF input and output ports of a conventional transversal multi‐band BPF to enhance its selectivity by adding poles and TZs without increasing its size. A compact integration concept using high‐Q 3D integrated‐passive devices (IPDs) is used for the realization of sub‐6‐GHz multi‐band BPFs. For practical validation purposes: (1) a tri‐band BPF with passbands centred at 1.58, 2.07, 2.83 Hz and fractional bandwidths (FBWs): 10.9, 9.06, 10% respectively and in‐band insertion loss (IL) between 2 and 2.8 dB and (2) a dual‐band BPF with passbands centred at 2 and 2.9 GHz with FBW 14.9% and 16.14% we manufactured and tested.