Water-soluble CdTe quantum dots (QDs) have been applied in various fields, such as photoluminescent imaging, labeling agents in immune analysis, heavy metal ion sensing, and solar cells. The synthesis of CdTe QDs has relied vastly on reactions between Cd2+ and Te2- ions in the presence of mercapto ligands. Te2- ions are usually formed in situ in the synthetic solution by reducing tellurite ions with hydride salts, such as NaBH4 which gives rise to the emission of highly explosive hydrogen gas. Herein, we report a novel method to synthesize CdTe QDs by using ammonia as a reducing agent. We demonstrate that under hydrothermal conditions, ammonia can reduce tellurite forming telluride ions which react with cadmium ions in the presence of glutathione forming CdTe QDs. The resultant QDs exhibited high photoluminescence and resolvable absorption. The synthetic method demonstrated herein could reduce the cost of CdTe-based quantum dots for rapid deployment.