Trough blowouts represent transport pathways for sediment through coastal dune systems. This paper documents seasonal differences in sand transport through a trough blowout. Measurements were made by trapping sand in Rosen-style traps installed at the mouth and crest of the parabolic dune and with erosion pins in the throat. Erosion-pin data indicated that the surface of the dune was generally accreting in late summer and eroding in winter, suggesting that the major loss of sediment from the dune was occurring in winter. The traps were emptied every 2–4 weeks and showed that, in general, more sand left the dune system than entered it. The amount of sand transported past the traps at the mouth of the dune varied seasonally, with smaller amounts during the summer months than in winter. The upper traps showed greater variability, but had more sediment transported in all months when compared with the lower traps. Amounts of sand transported during winter were greater than in summer.