This study was conducted to evaluate the effects of four different harvest times at 120, 140, 160 and 180 days after planting (DAP) on the tuberous yield and the tuberous quality of three purple sweet potatoes (PSP) from Vietnam (HL491) and two cultivars imported from Japan and Malaysia at 1 and 14 days after harvest. The results showed that the number of tuberous roots and the total yield increased over four harvest times but the highest marketable tuberous quantity and marketable yield of 20 tuberous roots/m2 and 16.7 tons/ha, respectively, were achieved at 140 DAP. The dry biomass and starch content of tubers increased with harvested time intervals from 140 to 180 DAP; while anthocyanin levels in tubers of all three cultivars were highest at 160 DAP. At 14 day post-harvest, while the contents of crude starch and anthocyanin tended lower than at harvest time, the tuberous dry biomass and total soluble sugars contents of all cultivars when harvested at 120 and 140 DAP increased slightly and achieved higher than those of other harvested times.