Measuring dispersal in rare sessile benthic species is important in the development of conservation measures such as MPA networks. However, efforts to understand dispersal dynamics for many species of conservation concern are hampered by a lack of fundamental life-history information. Here we present the first description of larvae of the fan mussel, Atrina fragilis, and examine key life-history traits that affect dispersal. Larval identification was accomplished using complementary molecular and morphologic techniques. Atrina-specific primers were designed by aligning Atrina COI sequences available in GenBank. As none of these were from UK specimens, primers were designed in the most conserved regions found across A. fragilis and its closest relative A. chautardi. A monthly time-series of zooplankton samples (2014–2015) suggests that A. fragilis follows the same pattern in spawning observed for other pinnids at temperate latitudes, with peak spawning in summer and winter. Average shell growth was estimated to be 6 μm d–1 based on presumed daily growth lines on larval shells. Measurements of the larval shell visible through the juvenile shell indicate a length of up to 770 μm at settlement. Using presumed daily growth lines, this translates into a pelagic larval duration of around 4 months.