The quality of mabé pearls from pearl oysters, Pteria sterna, produced in the Chone River Estuary, Ecuador, was evaluated. Adult oysters (70–75 mm total length) were grafted with half-pearl nuclei and then maintained in suspended culture conditions in lantern nets at a density of 20 organisms/level. Results showed that the culture conditions generated a great negative influence on the development of nucleated organisms, which resulted in high mortalities and little pearl production. Despite the high mortality, the oysters that managed to survive the second month (22%), produced mabé pearls with nacre thickness deposited on the top of the implanted nucleus close to 0.70 mm, the majority (>25%) being of intermediate quality (A and B), according to classic classification criteria (size, luster, impurities, roundness), followed by noncommercial pearls (10%–27%) and 15% high-AA quality mabé pearls. A small fraction was considered as gems (<5%). The mabé pearl production structure is like that produced in P. sterna cultivated in marine environments. The results show that in the Estuary of the Chone River, mabé pearls can be produced in 2 mo; however, production can be low due to high mortalities. It is recommended to carry out further research to minimize mortality and establish greater production feasibility.