Three representative monoterpenoid indole alkaloids isolated from the trunk barks of Winchia calophylla were investigated using electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in positive-ion mode. The major CID-fragmentation patterns are the neutral losses of H2O, CH3NH2 (C2H5N or C3H7N), CH2O, HCOOCH3 (HCOOH or CO2), and C4H6 molecules and CH3 radical. High-abundance radical ions at m/z 219, 217, and 205 are formed from corresponding precursor ions by loss of a CH3 radical. The product ion at m/z 168, 144, and 130 in the low-mass range are the characteristic ions of the indole part. A pair of isomers was distinguished unambiguously based on MS/MS spectra. The proposed fragmentation pathways were further supported by ESI-MS/MS/MS and D-labeling experiments.