The Mode I interlaminar fracture behavior of woven carbon fiber/epoxy composite laminates incorporating partially cured carbon nanotube/epoxy composite films has been investigated. Laminates with films containing carbon nanotubes (CNTs) in the as-received state and functionalized with polyamidoamine were evaluated, as well as laminates with neat epoxy films. Double-cantilever beam (DCB) specimens were used to measure G(Ic), the critical strain energy release rate (fracture toughness) versus crack length. Post-fracture microscopic inspection of the fracture surfaces was performed. Results show that initial fracture toughness was improved with the amino-functionalized CNT/epoxy interleaf films, but the important factor appears to be the polyamidoamine functionalization, not the CNTs. The initial fracture toughness remained relatively unaffected with the incorporation of neat epoxy and asreceived CNT/epoxy interleaf films. Plateau fracture toughness was unchanged with the use of functionalized CNT/epoxy interleaf films, and was reduced with the use of neat epoxy and as-received CNT/epoxy interleaf films. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2394-2405, 2011