Despite providing the opportunity for directly sensing molecular constituents with inherent fingerprint specificity in the 2.5-20 μm spectral regime, mid-infrared optical sensing technologies have not yet achieved the same penetration in waveguide-based chem/bio sensing compared to related sensing schemes operating at visible and near-infrared frequencies. In this review, current advances in mid-infrared chem/bio sensor technology will be highlighted and contrasted with the prevalent bottlenecks that have to date limited a more widespread adoption of mid-infrared sensing devices. However, with the increasing availability of advanced light sources such as quantum cascade lasers and the advent of on-chip semiconductor waveguide technologies, a prosperous future of this sensing concept for label-free detection in environmental analysis, process monitoring, and bioanalytics is perceived.