This study investigated the effects of dietary feruloyl oligosaccharides derived from fermented wheat bran (FOs-FWB) supplementation on carcase traits, meat quality, muscle fatty acid composition, and the expression of lipogenic genes in lambs. In a completely randomised design, 50 Dorper × thin-tailed Han lambs (20.21 ± 3.36 kg) were randomly divided into five treatments with ten replications. The lambs in the control group were fed a basal diet, while those in the experimental groups were fed the basal diet supplemented with 50, 100, 200, and 400 mg/kg FOs-FWB. The shear forces of longissimus dorsi (LD) in lambs fed 50 and 100 mg/kg FOs-FWB were significantly lower than that of the control group (p < .05). Lambs fed with 200 mg/kg FOs-FWB had higher crude protein and lower fat contents in LD muscle (p < .05), the ash content in LD muscle was increased by FOs-FWB supplementation (p < .05). Lambs fed 50 mg/kg FOs-FWB had significantly higher proportions of C18:1n − 9, C20:1, C18:3n − 3, C18:3n − 6 and total n − 3 (p < .05). The proportion of C18:3n − 6 was significantly increased by 100 mg/kg FOs-FWB supplementation (p < .05). Feeding 200 mg/kg FOs-FWB significantly decreased proportions of C14:0 and total saturated fatty acid (SFA), but increased proportions of C18:1n − 9, C18:2n − 6, total monounsaturated fatty acid (MUFA) and unsaturated fatty acid (UFA) to SFA ratio (p < .05). Moreover, increases in the proportion of C22:6n − 3 and total polyunsaturated fatty acid (PUFA) were observed in lambs fed FOs-FWB (p < .05). The relative expression levels of ACC, FAS, and SCD genes in the LD muscle of lambs fed 200 and 400 mg/kg FOs-FWB were higher than the control group (p < .05). Dietary supplementation with 100, 200, 400 mg/kg FOs-FWB significantly increased the relative mRNA expression level of LPL (p < .05). Furthermore, a decrease in the relative mRNA expression level of PPARγ was observed in lambs fed 50 mg/kg FOs-FWB (p < .05). In conclusion, dietary supplementation with FOs-FWB reduced shear force, enhanced intramuscular fat content and PUFAs proportion and stimulated lipogenic gene expression in LD muscle of lambs, especially at a level of 200 mg/kg addition. Highlights Dietary FOs-FWB improved the tenderness of the meat. Dietary supplementation with 200 mg/kg FOs-FWB increased the content of intramuscular fat and PUFAs, as well as the ratio of UFA to SFA. Dietary FOs-FWB affected the expression of genes related to lipid metabolism.