A new strychnobrasiline derivative, 12-hydroxy-10, 11-dimethoxystrychnobrasiline 1, has been isolated from the stem barks of Strychnos mattogrossensis. Its structure was established by spectroscopy analysis (1D and 2D NMR, MS, IR, UV) and literature data comparison. Two other known indoline alkaloids were also obtained from the heartwood, 12-hydroxy-11-methoxystrychnobrasiline 2 and strychnobrasiline 3.