This study presents the environmental boundaries and quality of the outer shelf Açu Reefs in northeastern Brazil by integrating multiple approaches including satellite images, bathymetry and backscatter imagery, surficial sediments, benthic foraminifera, and underwater surveys. The outer shelf is narrow, shallow, and steep (~6 km wide; 25–80 m deep), with sand bodies, valleys (~500 m wide and 15 m of relief), reef knolls, and ridges (~4 m height). Hard coral cover can reach ~17% (6 species; genus Montastrea, Siderastrea, Mussismilia, Madracis) and sponge cover was ~10% (16 species). Endemic Brazilian parrotfish were common (e.g., Scarus zelindae, Sparisoma amplum), but top predators were absent. Soft sediment habitats are well correlated with 65 foraminiferal species, which comprise a Caribbean-type reef community, including Buccella peruviana evidencing upwelling and nutrient enrichment. Although the benthic habitat is good, exhibiting suitable conditions for developing reef communities, reef fish assemblages indicate a declining trend based on quantitative data and an assessment of current threats.