A new lithocholic acid/IR 780 conjugate (LIC) was designed and synthesized for theranostic applications in triple-negative breast cancer. Lithocholic acid is an antitumor biomacromolecule and acts via multiple molecular targets. IR 780 iodide is a fluorescent NIR organic dye researched as a photothermal agent in cancer therapy. A combined conjugate, LIC can have wide applications as a Photothermal/chemotherapeutic and imaging agent in cancer therapy. LIC was characterized and evaluated for its photothermal cytotoxic effect in breast cancer cell lines. Further, to improve the bioavailability of the LIC, a polymeric (PLGA) nanosystem was developed and characterized. The resultant lithocholic acid/IR 780 polymeric nanoconjugates (LIPNCs) were well taken up by the cells and are evident by the inherent red fluorescence of LIC. The LIPNCs also exhibited commendable heat generation when exposed to NIR light (808 nm). The in-vitro anti-cancer studies of LIPNCs also revealed a significant NIR light-based photothermal efficacy (cytotoxic dose 0.75 μM) when compared to the free conjugate (LIC) or the parent moieties. Further cell-based fluorescent and molecular assays showed that LIPNCs induced ROS-mediated apoptotic cell death concurrently being physiologically biocompatible. In-vitro photoacoustic imaging of the LICs exhibited signals comparable to free IR780 dye. Future in vivo studies with LIPNCs or LIC may prove beneficial for developing a promising translational system for its wide application in image-guided cancer theranostics.