To investigate the effect of dietary sodium propionate (SP) on muscle metabolism and meat quality in lambs, 12 three-month-old Dorper (ewe) × Suffolk (ram) crossbred lambs with good body condition and a body mass of (22.70 ± 1.91) kg were selected and randomly divided into a control group (fed a basal diet) and an SP group (fed 20 g of SP per animal per day + a basal diet) for a 90-day feeding trial. After slaughter, the longissimus dorsi muscle was collected for the determination of fatty acid composition and muscle metabolic profiles using widely targeted metabolomics based on gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that dietary SP significantly increased the protein content in the longissimus dorsi muscle (P < 0.05), and decreased the redness, yellowness, pH_{45 min} and pH_{24 h} values (P < 0.05). Meanwhile, dietary SP significantly increased the contents of nonadecanoic acid, arachidic acid, heneicosanoic acid, cis-11-eicosenoic acid, cis-13,16-docosadienoic acid, cis-8,11,14-eicosatrienoic acid, and α-linolenic acid in the muscle (P < 0.05), and decreased the content of cis-10-pentadecenoic acid (P < 0.05). Widely targeted metabolomics analysis identified 1032 metabolites in the longissimus dorsi muscles of the two groups, among which 152 substances were significantly differential metabolites (SDMs). In the SP group, 3-iodo-L-tyrosine, (R)-2-hydroxy-3-phenylpropionic acid, lysophosphatidylserine (18:0), 5’-adenylyl sulfate, and DL-glyceraldehyde-3-phosphate were significantly upregulated. However, carnitine C_9:1, carnitine C_18:1, carnitine C_13:0, and carnitine C_9:0 were significantly downregulated. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that these SDMs were significantly enriched in metabolic pathways such as protein digestion and absorption, fatty acid elongation, amino acid biosynthesis, and unsaturated fatty acid biosynthesis. In conclusion, dietary SP may affect the metabolic homeostasis of lamb muscle by regulating amino acid and lipid metabolism via multiple signaling pathways and targets, thereby increasing muscle protein content, optimizing muscle fatty acid composition, and ultimately improving the eating quality and nutritional value of lamb meat.