Synopeas from New Guinea is revised, including 16 new species and four previously named species. The concepts for these species were developed in conjunction with a CO1 analysis that includes 16 New Guinean species and 3 Synopeas species from other regions. The molecular analysis determined that the New Guinea fauna does not form a clade, indicating multiple migrations. The following species are described and keyed: S. amandae Awad, sp. nov.; S. anunu Awad, sp. nov.; S. butterilli Buhl; S. codex Awad, sp. nov.; S. csoszi Buhl; S. kalubia Awad, sp. nov.; S. kiki Awad, sp. nov.; S. kira Awad, sp. nov.; S. klingunculum Awad, sp. nov.; S. luli Awad, sp. nov.; S. occultum Awad, sp. nov.; S. pattiae Awad, sp. nov.; S. psychotriae Buhl; S. pterocarpi Buhl; S. pulupulu Awad, sp. nov.; S. roncavei Awad, sp. nov.; S. sanga Awad, sp. nov.; S. toto Awad, sp. nov.; S. valavala Awad, sp. nov.; S. zhangi Awad, sp. nov. Leptacis pleuralis (Buhl), comb. nov. is transferred from Synopeas. Images of 56 holotypes of Synopeas are made publicly available online.