In this work, a novel dual-mode Substrate Integrated Coaxial Line (SICL) based bandpass filter operating at 28 GHz, targeted for 5G application is conceived. The proposed dual-mode bandpass filter is realized by exciting the degenerate modes in a corner-cut middle layer square patch by etching cross-shaped slots. The proposed filter exhibits a 12.25% 3-dB fractional bandwidth with a maximum 0.42 dB insertion loss in the passband. Frequency selectivity is enhanced by a transmission zero at 33.8 GHz which extends the out of band rejection up to at least 40 GHz. Further, the proposed SICL based cavity demonstrates a 46.75% size reduction as compared to its Substrate Integrated waveguide (SIW) counterpart. The superior electromagnetic compatibility of the proposed miniaturized SICL based dual-mode bandpass filter makes it an attractive option to deploy in millimeter-wave range. © 2018 IEEE.