The naupliar development of the barnacle Balanus spongicola is described, from larvae reared in the laboratory. The planktotrophic nauplii of B. spongicola reached the cyprid stage 11 days after hatching, at 20°C, and only eight days after hatching, at 25°C. Larval development includes six naupliar and one cyprid stage, following the typical pattern of the thoracican Cirripedia. Naupliar stages have a broad pear-shaped cephalic shield with a straight anterior margin and a pair of fairly short posterior spines in stages IV–VI. Dorsal and marginal spines are absent. Frontolateral horns are of medium length, directed forward from stage III. Small teeth on the median labral lobe found in some warm-water species are only weakly pronounced. The arrangement of abdominal spines and larval setation are in the usual balanoid pattern. The larvae of B. spongicola share some features with earlier described nauplii of Solidobalanus fallax, a non-native UK species inhabiting British waters. Balanus spongicola, however, possess more typical balanoid larvae. Its nauplii are more elongated (the cephalic shield is longer than broad). Thoraco-abdominal processes and posterior shield spines in B. spongicola are shorter than those in S. fallax. The abdominal process remains shorter than the dorsal thoracic spine until stage VI in B. spongicola but becomes nearly equal in S. fallax.