Two new functionalized ergostane-type steroids, phomopsterones A (1) and B (2), were isolated from the plant-derived Phomopsis sp. TJ507A. Their structures were determined on the basis of spectroscopic data, a modified Mosher's method, X-ray crystallographic analysis, and quantum chemical calculations. Compound 1 is an unprecedented ergosteroid featuring a rearranged bicyclo[3.3.1]nonane motif resulting from B-ring scission and a subsequent 180° rotation of the ring A during biosynthesis. Compound 2 exhibited anti-inflammatory activity.