During screening of marine actinomycetes for anti-mycobacterial activity, a new phenoxazine derivative (1) was isolated, along with 6-phenazinediol (2), 6-methoxy-1-phenazinol (3), nocardamin (4), and 3-pyridinecarboxylic acid (5), from a culture of Nocardiopsis sp. 236 collected from the west Pacific. The chemical structure of 1 was established on the basis of 1D-, 2D-NMR, and HRQ-TOF MS data. All compounds were evaluated for their anti-mycobacterial activity in vitro, and only compounds 2 and 3 exhibited weak activity.