Energy deficiency in the diet may delay the resumption of ovarian post-partum activities. Hence, this study aims to determine the effects of varying metabolize energy (ME) of lactating Dorper ewes on blood serum progesterone. This study was conducted at Agropolitan Besut-Setiu, Terengganu for 180 days feeding trial. Twenty (20) lactating Dorper ewes (mean initial body weight: 50.89±2.19; 7 years old) were randomly assigned to four groups with five (5) animals each, based on randomized complete block design (RCBD). The control was fed with a basal diet consisted of Napier grass (Pennisetum purpureum) and commercial breeder pellet. In contrast, treatments diet consisted of lactating ration in the total mixed ration (TMR). The metabolise energy (ME) (MJ/kg DM ME) were varied at 11, 9, 10 and 12 for CON11, LR9, LR10 and LR12, respectively. The serum progesterone concentration was monitored weekly, starting from one-week post-partum for 10 weeks by enzyme-linked immunosorbent assay (ELISA). There were significant differences (p<0.05) of progesterone concentration of ewes at week 4, week 7 and week 9 of the feeding trial. The increased level of ME in the diet also leads to linear increased (p<0.05) of serum progesterone concentration. It also shows that the shortest period of ewes that reach the threshold value of 1 ng/ml was in LR10 (week 4), followed by LR12 (week 5) and CON11 and LR9 at week 7 of the feeding trial. Hence, the finding of this study revealed that feeding of 10 MJ/kg DM ME is adequate to accommodate the energy requirement of lactating Dorper ewes and reduce the time ovarian cyclicity resumption after parturition.