We tested competing theories on the origins of the New Zealand fauna using thomisid spiders as a model group. These theories can be broadly described as old and vicariant versus young and recent (dispersal). To test these theories, a phylogenetic analysis was undertaken based on cytochrome c oxidase subunit I (COI) and 28S rRNA sequence data, with smaller datasets (histone H3, nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 1 and a combined dataset) used to improve resolution of internal branches. The monophyly of New Zealand thomisid subfamilies and of individual taxa were also assessed using these data. Our data supports the separation of New Zealand clades from their Australian counterparts. Evidence of recent dispersal to New Zealand by Australian stephanopines combined with our proposed maximum divergence date of 5.3 mya indicates that the New Zealand thomisids are a younger lineage than previously suspected. Several other gene targets (internal transcribed spacer units 1 and 2, wingless and 18S rRNA) were examined but did not generate sufficient reliable data to contribute to the analysis. Corrected p-distance values for COI indicate that Sidymella angularis, a widely distributed and morphologically variable stephanopine species, is a single taxon. Three undescribed endemic species exhibited molecular and morphological distinctiveness from previously described New Zealand thomisids.