Lecanora sorediomarginata Rodrigues, Terrón & Elix sp. nov., described as new to science from Portugal, is characterized morphologically by a crustose whitish-grey to greenish thallus developing soralia from small, marginal warts and chemically by the presence of 3,5-dichloro-2′-O-methylnorstenosporic acid [major], 3,5-dichloro-2′-O-methylanziaic acid [minor], 3,5-dichloro-2′-O-methylnordivaricatic acid [minor], 5-chloro-2′-O-methylanziaic acid [trace], atranorin [minor], chloroatranorin [minor], and usnic acid [trace]. It is chemically similar to L. lividocinerea, to which it shows phylogenetic affinities based on ITS rDNA sequence analysis, and to L. sulphurella. Lecanora sorediomarginata is epiphytic on Pinus pinaster and P. pinea, in pine forests on sand dunes along the Portuguese coast.