Perinatal maternal high-fat diet (HFD) increases susceptibility to obesity and fatty liver diseases in adult offspring, which can be attenuated by potent hypolipidemic action of fish oil (FO), an n-3 polyunsaturated fatty acid source, during adult life. Previously, we described that adolescent HFD offspring showed resistance to FO hypolipidemic effects, although FO promoted hepatic molecular changes suggestive of reduced lipid accumulation. Here, we investigated whether this FO intervention only during adolescence period could impact the offspring metabolism in adulthood. Then, female Wistar rats received isoenergetic, standard (STD:9% fat) or high-fat (HFD:28.6% fat) diet before mating, and throughout pregnancy and lactation. After weaning, male offspring received standard diet; and from 25- to 45 days-old they received oral administration of soybean oil (SO) or FO. At 150 days-old, serum and hepatic metabolic parameters were evaluated. Maternal HFD adult offspring showed increased body weight, visceral adiposity, hyperleptinemia and decreased hepatic pSTAT3/ STAT3 ratio, suggestive of hepatic leptin resistance. FO intake only during adolescence period reduced visceral adiposity and serum leptin, regardless of maternal diet. Maternal HFD promoted dyslipidemia and hepatic triglyceride accumulation, which was correlated to reduced hepatic CPT-1a content, suggesting lipid oxidation impairment. FO intake did not change serum lipids; however, it restored hepatic triglyceride content and hepatic markers of lipid oxidation to STD offspring levels. Therefore, we concluded that FO intake exclusively during adolescence programmed STD offspring and reprogrammed HFD offspring male rats to a healthier metabolic phenotype at adult life, reducing visceral adiposity, serum leptin and hepatic triglycerides content in offspring adulthood.