Current anticancer treatments, including recently approved anticancer nanomedicines, suffer from many limitations, including a low targeting efficiency and the development of multidrug resistance leading to a lack of efficacy. This thesis aimed to develop theranostic multidrug nanoparticles (NPs) to treat cancer. Firstly, we designed squalene-near infrared dye (Sq-NIR Dye) NPs that demonstrated specific cancer targeting, fluorescence imaging, and antitumour properties via photodynamic/photothermal therapy. Secondly, we combined Sq-NIR Dye with thymoquinone (TQ), a phytochemical compound with anticancer properties. The obtained Sq-NIR Dye/TQ NPs were tested in vitro and in vivo in prostate cancer. In vivo experiments in the chicken chorioallantoic membrane (CAM) demonstrated an effective tumour uptake of our two nanoformulations and an enhanced antitumour effect of Sq-NIR Dye/TQ NPs compared to Sq-NIR Dye NPs. This thesis gave a proof of concept that theranostic multidrug NPs for photodynamic/photothermal therapy is effective in a CAM model and deserve further preclinical testing.