The seahorse has been used for thousands of years as an important traditional Chinese medicine (TCM) in China. Many species of wild seahorse have become endangered, but demand for them continues to grow rapidly. Therefore, it is urgent to cultivate seahorses to relieve the strain on natural populations and meet the market demand for this TCM. In this study, medicinal components of wild and cultured yellow seahorses (Hippocampus kuda Bleeker) were analysed and compared. Different parts of the body (cortex and bone), male and female specimens, and seahorses of different ages were analysed. Crude protein, crude fat, trace elements, calcium, amino acid, fatty acid, steroid and cholesterol content were measured. The results showed that moisture content accounted for 70% of wet weight and ash content increased with growth. Crude protein and fat contents were higher in cultured seahorses than in wild specimens, and the content of Zn in cultured seahorses (93.26 ± 10.44%) was significantly higher than that of same‐aged wild seahorses (74.20 ± 3.83%). Amino acid and fatty acid contents of cultured seahorses also were higher than those of wild seahorses. These findings show that cultured seahorses can also be used in TCMs and that 1‐year‐old cultured seahorses have the best properties.