A new peltate-leaved taxon of Psacalium, Psacalium putlanum, is described and illustrated from southwestern Oaxaca, Mexico. It appears to be closely related to the widespread P. peltigerum. Additionally, the closely related P. peltigerum var. latilobum Pippen of Guerrero is elevated to specific rank as P. latilobum (Pippen) B.L. Turner. A phototype and drawing of P. putlanum are provided, along with a map showing the distribution of the taxa concerned.