A new isoflavone, milletenol A (1), along with four known flavonoids (2–5) were isolated from the seeds of Millettia pachycarpa. The structure of 1 was established by extensive spectroscopic methods while known compounds were identified by comparisons with literature data. Compound 1 and 2 showed significant anti-inflammatory activities against nitric oxide production in LPS-induced RAW264.7 macrophages. The state of CuSO-stimulated inflammation was effectively alleviated by compound 1 in zebrafish. However, no significant cytotoxicity against human breast cancer cells was observed among all isolates.