Agaricus is a large genus of mushrooms with having great number of edible species. Subgenus Minores sect. Minores contain the richest species diversity. A new species Agaricus totalaiiensis described based on morpho-anatomy and molecular data analyses. It is characterized by small to medium-sized basidiomata that are initially parabolic to convex, becoming planate to concave at maturity, dull red or purplish-red to reddish brown at the center with a pale margin, become too red at the center become reddish brown to light radish brown margin at maturity, and large ellipsoid basidiospores. Molecular phylogenetic analyses based on ITS sequences confirmed its identity as a new taxon nested within the subgenus Minores sect. Minores.