Treefrogs in the family Hylidae make up almost 40% of the anurans in Mexico; however, beyond monographic work published >50 yr ago, we still know very little about their reproductive ecology. Herein, we investigated reproductive traits and compared life-history patterns among three hylid treefrogs distributed along Mexico's Pacific Lowlands, a biogeographically unique faunal region threatened by sea level rise. We examined museum specimens of the Mexican Leaf Frog (Agalychnis dacnicolor, n = 200), the Lowland Burrowing Frog (Smilisca fodiens, n = 340), and the Mexican Shovel-headed Treefrog (Triprion spatulatus, n = 336) collected during 1902–1965 from nine Mexican states. Adult males were smaller than females in all three species. Testes were largest in July and August, and gravid females were most common during July–August and largely absent by September. Juveniles were present from July to September. Gravid females exhibited positive relationships between body size and clutch size, with larger A. dacnicolor females also having larger eggs. Growth was difficult to discern because most samples were seasonally restricted, but unpublished collectors' notes revealed rapid growth to metamorphosis in T. spatulatus. Geographic variation in body size exhibited opposite patterns between A. dacnicolor and S. fodiens, whereas T. spatulatus had no clear relationship with geography. We provide the most comprehensive data on reproduction for these three treefrog species to date, including the first clutch size estimates for two of them addressing critical gaps in their life history and paving the way for a more complete understanding of life-history variation in Mexican hylids.