Three hundred seventy lizards representing 6 families (16 species)—Corytophanidae: common basilisk, Basiliscus basiliscus (n  =  9); green basilisk, Basiliscus plumifrons (n  =  3); Smooth helmeted iguana, Corytophanes cristatus (n  =  8); Gekkkonidae: yellow-headed gecko, Gonatodes albogularis (n  =  63); common house gecko, Hemidactylus frenatus (n  =  53); yellowbelly gecko, Phyllodactylus tuberculosus (n  =  10); Iguanidae: Oaxacan spinytail iguana, Ctenosaura quinquecarinata (n  = 2); black iguana, Ctenosaura similis (n  =  37); Phrynosomatidae: rosebelly lizard, Sceloporus variabilis (n  =  18); Polychrotidae: water anole, Anolis aquaticus (n  =  5); neotropical green anole, Anolis biporcatus (n  =  7); copper anole, Anolis cupreus (n  =  51); humble anole, Anolis humilis (n  =  26); lion anole, Anolis lionotus (n  =  72); swift anole, Anolis tropidolepis (n  =  2); Teiidae: rainbow ameiva, Ameiva undulata (n  =  4)—collected in the Area de Conservación Guanacaste, Costa Rica, were necropsied. Gravid nematodes representing 14 species—Africana telfordi, Cosmocercoides variabilis, Cyrtosomum penneri, Cyrtosomum scelopori, Falcaustra costaricae, Oswaldocruzia costaricensis, Ozolaimus monhystera, Physaloptera retusa, Piratuba digiticauda, Rhabdias nicaraguensis, Skrjabinelazia galliardi, Skrjabinodon scelopori, Spauligodon oxkutzcabiensis, Strongyluris panamaensis—and larvae representing 2 species—Acuariidae gen. sp. Ascarididae gen. sp.—were found. Thirty-two new host records are reported.