The phylogeny of the Agathidinae is analyzed employing 45 agathidine genera, 172 Agathidinae operational taxonomic units, and sequences from the mitochondrial gene COI and the nuclear ribosomal gene 28S. The tribal classification is revised; two new tribes are proposed, i.e., Lytopylini and Agathirsini. Mesocoelini n. stat., is included as a tribe of Agathidinae for the first time. The concepts of Earinini and Agathidinini are revised. Biroia Szépligeti, 1900, is synonymized with Megalagathis Schulz, 1906 (emendation for Megagathis Krechbaumer 1894). A new genus and species from Colombia, Smithagathis davidsmithi Sharkey are erected. The currently recognized 61 genera of Agathidinae are presented in a list which includes their tribal placement. Biroia Szépligeti, 1900, and its junior synonym Isoptronotum Enderlein, 1920 are synonymized with Megalagathis Schulz, 1906, new synonymies. The species of Biroia are moved to Megalagathis as new combinations.