A new chloro-depsidone (1) and five known compounds, variolaric acid (2), lecanoric acid (3), alpha-alectoronic acid (4), atranorin (5), and ergosterol peroxide (6), have been isolated from the lichen Ochrolechia parella. The structure of compound 1 was elucidated by spectroscopic analysis. Additionally, the tautomeric equilibrium of compound 4 was investigated. In the present study, two specimens of this lichen, growing under different light conditions, were analyzed. The major compound in both samples was found to be 2, but the amount of this metabolite was significantly higher in the shaded specimen (0.76% w/w). The new compound parellin (1) predominated in the specimen grown under shady conditions, while atranorin (5) was found only in the sunlit specimen. The cytotoxic activities of 2, 4, and 6 against B16 melanoma cells were evaluated.