This study aimed to evaluate and analyze the effects of a flushing diet containing DHA and EPA from Lemuru fish oil on the reproductive performance parameters of Garut ewes. Forty (n = 40) primiparous Garut ewes aged 12–14 months with a body weight of 28.92 ± 4.94 kg were assigned into four experimental treatment groups. The experimental diets contained roughage : concentrate (30:70%) designated as control concentrate (CNT), flushing concentrate with 6% palm oil (PO), flushing concentrate with 3% palm oil mixed with 3% lemuru oil as DHA and EPA sources (PFO), and flushing concentrate with the addition of 6% lemuru oil (FO). Treatment animals were fed two weeks before and after conception and parturition (8 weeks of total flushing treatment). The addition of fish oil at either 3% (PFO) or 6% (FO) resulted in significantly higher reproductive performance of ewes by increasing the litter size, as reflected by the birth of multiple kids (P < 0.05) compared to CNT and PO. Adding fish oil (PFO and FO) also maintains gestation, resulting in increased kid yield, especially in the FO treatment, which yields the highest kid yield (0% single kid birth). The male ration lamb was also higher with fish oil supplementation (PFO and PO) (P < 0.05). Supplementation with fish oil could also maintain progesterone levels during the gestation period and some biochemical blood parameters. This study showed that using Lemuru fish oil 6% (FO) with a concentration of 1.34% DHA and EPA overall led to significantly higher reproductive performance in Garut sheep.