The feeding ecology of larvae of the lightfish Maurolicus parvipinnis ( Pisces: Sternoptychidae, 2.8-13.4 mm) in fjords and channels of southern Chile (41 degrees-53 degrees S), was analysed during austral spring 2005, 2008 and 2009. Larvae of M. parvipinnis begin external feeding at similar to 3-mm body length (BL). They are carnivorous predators with similar feeding incidence during day and nighttime, but with higher prey numbers in their guts during day than night. Feeding incidence increased after 8-mm BL, coinciding with an increase in the growth rate of the upper jaw length. The diet of M. parvipinnis larvae was composed of 22 different prey items, mainly invertebrate eggs, nauplii, calanoid, cyclopoid and poecilostomatoid copepodites, ostracods, cladocerans and amphipods. According to the relative importance index [% index of relative importance (IRI)], the most important prey items were Paracalanus parvus copepodites (% IRI 55.6%), Oithona spp. copepodites (% IRI 16.3%) and copepod eggs (% IRI 9.2%), indicating that most of the feeding is on copepod early life stages. Trophic niche breadth was similar to 0.17 and it did not increase with larval length, suggesting that larval M. parvipinnis have a high degree of selective foraging. Also, we detected a significant relation between feeding success and vertical stratification of the water column, with higher prey volume per gut found in larvae collected in areas with a Brunt-Vaissala frequency of 0.07-0.2 cycles s(-1). We discuss potential effects of the fjord environment on the feeding behavior of this important species along Chilean Patagonia.