This article provides an overview of the development and applications of plasmonics-active nanoprobes in our laboratory for chemical sensing, medical diagnostics and therapy. Molecular Sentinel nanoprobes provide a unique tool for DNA/RNA biomarker detection both in a homogeneous solution or on a chip platform for medical diagnostics. The possibility of combining spectral selectivity and high sensitivity of the surface-enhanced Raman scattering (SERS) process with the inherent molecular specificity of nanoprobes provides an important multiplex diagnostic modality. Gold nanostars can provide an excellent multi-modality platform, combining two-photon luminescence with photothermal therapy as well as Raman imaging with photodynamic therapy. Several examples of optical detection using SERS and photonics-based treatments are presented to illustrate the usefulness and potential of the plasmonic nanoprobes for theranostics, which seamlessly combines diagnostics and therapy.