The Alagoas Antwren (Myrmotherula snowi) is a Critically Endangered endemic bird restricted to the Pernambuco Center of Endemism. It is currently restricted to a single forest fragment—the Murici Ecological Station in Alagoas. Its population is currently estimated at less than 30 individuals. Moreover, little is known about the natural history of this species. Since 2010 this bird has been annually monitored, but its nests have never been found. We carried out 131 expeditions to this forest fragment between August 2010 and November 2018. During this period, we captured and marked 11 adults and 7 juveniles. However, it was not until 9 November 2018 that the first nest was discovered. The nest was a deep cup composed of black fungal rhizomorphs with small fragments of dried leaves on the outer side. It was suspended on a horizontal fork of a young plant, 1.7 m above the ground. The eggs were oval in shape, light beige in color with reddish patches distributed throughout the egg and most concentrated in the rhombic pole. The eggs measured 1.53 × 1.02 and 1.54 × 1.03 cm. The nest was monitored, but on 25 November 2018 we found the nest empty; we deduced that it had been preyed upon. Subsequently, we found 3 more nests. However, in our efforts over the most recent 11 expeditions (1 year and 3 months after the original nest discovery until February 2020), we failed to find any additional nests. Our records of juvenile individuals indicate they are still reproducing in the area and represent a possibility to recover this species. However, the strong predation pressure in the area and the absence of mixed flocks are concerning. We urge actions to protect its nests, recompose mixed flocks, translocate individuals to nearby habitat patches, and attempt captive breeding, among efforts that should be evaluated.