Quantum Dots (QDs) are mainly considered semiconductor nanoparticles (NPs) with a size of less than 10 nm. They have generated great enthusiasm in the field of materials science because of their unique size-dependent, electronic, optical and structural properties, chemical stability, and special traits such as photoluminescence activity and quantum confinement effect. Intense concerns have been raised on the toxicity assessment of QDs because most QDs belong to group II–VI (CdTe, CdS, CdSe), and group III−V elements (InP, InAs), which contain heavy metals that pose a threat to human beings as well as the environment. This chapter critically evaluates the emerging class of metal oxide QDs (MOQDs), including ZnO, SnO2, Co3O4, and CeO2, which are relatively less/non-toxic compared to conventional QDs comprising selenide, telluride, arsenide, etc. This chapter explores advances in various synthesis methodologies, such as top-down and bottom-up approaches, and their influence on the properties of semiconductor metal oxide-based QDs. A comprehensive analysis of the various applications of MOQDs, like photocatalytic degradation of organic pollutants, and hydrogen generation has been conducted. Using fluorometric analysis, much information has been gathered by sensing different sorts of heavy metal ions (Hg2+, Pb2+, Cd2+, Cr2+, etc.), VOCs and organic pollutants. The ongoing challenges and future perspectives for semiconductor metal oxide QDs have also been scrutinized. A piece of deep information about the ongoing state of the art in semiconductor metal oxide-based QDs research and the potential for future developments have been analyzed thoroughly. This chapter sheds light on the various synthesis methodologies, properties, and applications of the semiconductor metal oxide quantum dots (MO QDs).