This study investigated the effects of material particle size, irradiation time, extraction temperature, type of solvents, ethanol composition, and the ratio of liquid-to-sample on microwave-assisted extraction (MAE) of roots of Morinda citrifolia to obtain the most important anti-cancer compound, damnacanthal. The highest recovery of the compound was obtained after 5 min of MAE of small particle size material at 100 and 120 degrees C. Longer extraction time caused the decrease in percent recovery due to the decomposition of the compound. Among the pure solvents tested, acetone and methanol gave the highest recovery. However, the use of ethanol-water solution (80% v/v) could considerably improve the yield of damnacanthal extracted. MAE was found to give the highest extraction efficiency when compared with other extraction methods such as extraction with electrical heating, soxhlet extraction, and ultrasound-assisted extraction (UAE).