This study evaluated the effect of different medium-chain to long-chain fatty acid (MCFA/LCFA, M/L) ratios on growth performance, intestinal function, antioxidant capacity, and gut microbiota in piglets. A total of 250 piglets were randomly assigned to five groups with five replicates, each containing ten pigs. The diets, containing varying amounts of MCFA-rich coconut oil and LCFA-rich soybean oil, resulted in M/L ratios of 0, 2.1%, 4.2%, 8.8%, and 33.8%. Results showed that both final body weight and average daily weight gain increased as the M/L ratio increased (P < 0.05), while the 8.8% M/L ratio diet exhibited the lowest feed-to-gain ratio (P < 0.05). As the M/L ratio increases, the contents of SOD and GSH-Px were increased and MDA was decreased in serum (P <0.05). The 8.8% and 33.8% M/L diets improved ileal and jejunal morphology (P < 0.05), as indicated by greater villus height and villus height/crypt depth ratios. Furthermore, increasing M/L ratios from 0 to 33.8% increased expression of tight junction proteins occludin and ZO-1 in the jejunum (P < 0.05). The 33.8% M/L ratio reduced microbial α-diversity (P < 0.05), while 8.8% M/L diet significantly increased the abundance of beneficial bacteria (e.g., Lactobacilli, Prevotella) and decreased harmful bacteria (e.g., Escherichia-Shigella, Enterococcus) in the cecum (P < 0.05). In summary, our study found that 8.8% of dietary M/L ratios significantly improved growth performance, likely through modulating intestinal function, antioxidant activity, and gut microbial composition.