The current research demonstrates the feasible biomedical application of AuNPs coated with doxorubicin (Dox)-loaded fucoidan (Fu) for dual-chemotherapy and photothermal treatment (PTT) on eye tumors in vitro and in vivo. Marine-derived Fu was used as a capping agent to achieve high photostability for AuNPs, and Dox as a FDA-approved anti-cancer drug was added to induce chemotherapy. The synthesized Dox-Fu@AuNPs exhibited high cytotoxicity on the tumor cells and strong light absorption for temperature increase in vitro. After intratumoral injection of Dox-Fu@AuNPs in the rabbit eye tumors, PTT-assisted Dox-Fu@AuNPs entailed the complete removal of the eye tumors without recurrence for 14 days after the treatment. Photoacoustic image contrast from the tumor regions was enhanced due to selective light absorption by the administered Dox-Fu@AuNPs. Therefore, the proposed Dox-Fu@AuNPs can be a potential nano-theranostic material for treating and diagnosing the eye tumors.