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Investigation of the 95% EtOH extract of stems of Dendrobium findlayanumafforded four new seco-dendrobines, findlayines A–D (1–4); two known dendrobines, dendrobine (5) and 2-hydroxydendrobine (6); and four new phenolic compounds, dendrofindlaphenols A–C (7, 9, and 10) and 6″-de-O-methyldendrofindlaphenol A (8). Compounds 1and 2are the first seco-dendrobines possessing a seven-membered lactam moiety, with 3and 4derived from the oxidative cleavage of the C-2–C-3 bond of dendrobine. The structures were established using spectroscopic methods and by comparison with literature data. The absolute configurations of 1–4were confirmed via single-crystal X-ray diffraction data. Cytotoxic activity assays against HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines revealed IC50values ranging from 2.3 to 5.3 μM for compound 7, from 19.4 to 34.4 μM for 8, and from 49.4 to 96.8 μg/mL for the EtOAc extract. An assay of the inhibition of NO production with RAW 264.7 cells indicated that 8had an IC50value of 21.4 μM, and the EtOAc extract, 10.5 μg/mL. The EtOAc extract possessed DPPH radical scavenging activity of 69.93% at 100 μg/mL.