The species was first described in 1951 by the French mycologist Robert Kühner as Hygrophorus quietus and was later moved to the genus Hygrocybe.
The species was originally named Hygrophorus virescens by American mycologists Lexemuel Ray Hesler and Alexander H. Smith in their 1963 monograph of North American Hygrophorus species.
In their 1963 monograph of the Hygrophorus of North America, American mycologists Lexemuel Ray Hesler and Alexander H. Smith classified H. agathosmus in the subsection Camarophylli, a grouping of related species characterized by a dry stem, and the absence of a gelatinous outer veil.
The species was first described officially by American mycologists Lexemuel Ray Hesler and Alexander H. Smith in their 1963 monograph on North American Hygrophorus species.