Cinnamaldehyde (CA) is a potential substitute for antibiotic growth promoters in animal breeding. In this study, we investigated its effects as a dietary supplement on growth performance, serum antioxidant capacity, intestinal digestive enzyme activities, intestinal morphology, and caecal microbiota in meat rabbits. Weaned meat rabbits ( = 450) were randomly assigned to five groups, Groups A, B, C, D, and E, and fed 0, 50, 100, 150, and 200 mg/kg CA diets, respectively, for 47 days. Biological samples including serum (antioxidants), duodenal/caecal content (enzymes), intestinal tissue (morphology), and caecal digesta (microbiota) were collected at day 47 postweaning for analysis. Groups C and D showed significantly higher final body weights than Group A, with Group D (150 mg/kg CA) demonstrating superior growth performance including 11.73% longer duodenal villi ( < 0.05), 28.6% higher microbial diversity ( < 0.01), and 62% lower diarrhoea rate versus controls. Digestive enzyme activity as well as serum antioxidant capacity increased with increasing CA dose, Microbiota analysis revealed CA increased fibre-fermenting Oscillospiraceae (+38%, < 0.01) while reducing Ruminococcaceae (-27%, < 0.05). Thus, dietary CA supplementation at 150 mg/kg was identified as the optimal CA dose for improving meat rabbit production. These findings highlight CA as a functional feed additive for promoting sustainable rabbit production.