This study describes a new record of a thelotremoid lichen (Leucodecton desquamescens) from South Korea. The taxon is characterized by thick, bulging thallus with many calcium oxalate crystal inclusions; an immersed, round to irregular ascomata with free exciple, ellipsoid to $pm$ roundish submuriform, brown ascospores, and lack of secondary metabolites. A detailed taxonomic description and comments are presented for this taxon. The lichen genus Leucodecton is reported for the first time in South Korea.