The Barataria Estuary, Louisiana, is an interconnected hydrologic network of bayous, canals, lakes, and bays that stretches from freshwater swamps to the open Gulf of Mexico along a salinity gradient. Although the Barataria Estuary was built by sediment delivered via distributaries and interdistributaries of the Mississippi River, flood protection activities have blocked the historical connections between the Mississippi River and the upper estuary. Blue crabs (Callinectes sapidus) are abundant in the Barataria Estuary and seasonally occur in the upper estuary. To gain a better understanding of the blue crab seasonal dynamics in the upper Barataria Estuary, this study was designed to: 1) document the summer and fall abundance and distribution of blue crabs, 2) describe the size and condition of the blue crab population, and 3) determine if water quality affects blue crab abundance and distribution. Seven fixed sites were sampled at least biweekly with modified commercial crab traps from 11 July 2006 to 6 December 2006. Males (n = 591) were more abundant than females (n = 58). Although mean carapace width was greater for females than males, female and male blue crabs had a similar mean carapace length, total weight, and condition factor. Blue crabs were most abundant in July and August, decreased through the fall, and no crabs were collected after 7 November 2006, once temperature had dropped below 15 C. Low temperatures (15 C) and the occurrence of hypoxic conditions (dissolved oxygen ≤2.0 mg/L) limit summer and fall abundance of blue crabs in the upper Barataria Estuary. Future conservation and restoration activities should include strategies to reduce the periodic occurrence of hypoxia in the upper Barataria Estuary and maintain upper and lower estuary connectivity.