To mitigate stress associated with early weaning, modification of sow feeding may indirectly improve the intestinal microbial community in suckling piglets. This study aimed to determine the effects of medium-chain triglycerides (MCT) supplementation, alone or in combination with β-hydroxy-β-methylbutyric acid (HMB), on parturition performance, lipid metabolism, and milk composition in sows, as well as on growth performance and intestinal microbiota in piglets, from day 110 of gestation until day 14 postpartum. Thirty multiparous sows (Large White × Landrace) in late gestation (parity 2–3) were assigned to three treatment groups: control (basal diet), MCT (basal diet supplemented with 14.3 g MCT), and MCT+HMB (basal diet supplemented with 14.3 g MCT and 2 g HMB). Compared with the control group, the MCT and MCT+HMB groups had significantly shorter labour durations, lower serum interleukin-6 and C-reactive protein concentrations, higher milk fat and protein contents in colostrum, and protein in mature milk, also a higher average daily gain in suckling piglets (P < 0.05). Compared with the MCT group, supplementation with MCT+HMB resulted in a higher number of live-born piglets, increased milk protein and fat contents in mature milk, and elevated levels of medium-chain, long-chain, and n-3 polyunsaturated fatty acids in colostrum (P < 0.05). Both treatment groups showed a lower relative abundance of harmful bacteria (Bradyrhizobium and Shigella spp.) and a higher relative abundance of beneficial bacteria (Bacteroides anomalies and Enterococcus faecalis). These findings suggest that the concurrent supplementation of MCT and HMB is more beneficial for sow productivity and piglet growth performance compared to MCT supplementation alone.