Portions of two stocks of northern sea otters (Enhydra lutris kenyoni) occur in Lower Cook Inlet (LCI), Alaska. Sea otters on the west side of LCI are considered part of the southwest Alaska stock; sea otters occupying eastern LCI are considered part of the southcentral Alaska stock. Information concerning the distributions and abundance of sea otters in LCI is needed to track the status and trends of these populations and address management concerns associated with oil and gas exploration and coastal development in the region. In May 2017, we conducted a series of replicate aerial surveys of sea otters across LCI following the methods of Bodkin and Udevitz (1999). Our abundance estimate for western LCI (southwest Alaska stock) was 10,737 (SE = 2,323) sea otters. Sea otters were not uniformly distributed across western LCI. The highest sea otter densities (up to 8 sea otter/km2) occurred within Kamishak Bay to the west and north of Augustine Island. Sea otter densities were relatively low north of Kamishak Bay. The total abundance estimate for eastern LCI (part of the southcentral Alaska stock) was 9,152 (SE = 1,020) sea otters. The highest densities of sea otters in eastern LCI were found along the north shore of Kachemak Bay and in Port Graham. We also found large numbers of sea otters along the eastern shore of LCI between Anchor Point and Clam Gulch. We recommend conducting a sea otter distribution survey in September, prior to the appearance of sea ice, and again during winter to examine potential seasonal shifts in sea otter distributions in LCI.