The green synthesis of metal oxide nanoparticles (NPs) has garnered considerable attention from researchers due to its utilization of eco-friendly solvents during synthesis and cost-effective approaches. This study focuses on the synthesis of titanium oxide (TiO₂) and dopamine (DA) carboxymethyl cellulose (CMC)-doped TiO₂ (DA/CMC/TiO₂) NP using Psidium guajava leaf extract, while also investigating the structural, optical, and morphological and biocidal potential of the prepared NPs. Significantly larger zones of inhibition were observed for DA/CMC/TiO₂ NPs compared to TiO₂ against various pathogens. Moreover, the MTT assay was carried out to evaluate the anticancer activity of the prepared samples against MG-63 cells, and the results revealed that DA/CMC/TiO₂ NPs exhibited significantly higher level of anticancer activity compared to TiO₂. The experimental results demonstrated that DA/CMC/TiO₂ NPs exhibited enhanced anticancer activity in a dose-dependent manner when compared to TiO₂ NPs.