Tendon calcification is a common but intractable problem leading to pain and activity limitation when injury or tendinopathy progresses into the late stage. This is because tendon stem/progenitor cells (TSPCs) can undergo aberrant osteogenic differentiation under inflammatory conditions. This study aims to investigate the effect of curcumin, a natural anti-inflammatory agent, on regulating the differentiation of TSPCs in tendon calcification. With inflammatory stimulation, TSPCs showed higher alkaline phosphatase activity and more frequent formation of mineralized nodules which were verified in the culture system; however, curcumin significantly alleviated these pathological changes. In in vivo function analysis, chitosan microsphere-encapsulated curcumin was delivered to injured sites of rat tendon ectopic calcification model. The inflammation in the tendon tissues of the curcumin group was significantly relieved. Controlled-release curcumin partially rescued tendon calcification and enhanced tendon regeneration in animal model. This study demonstrates that controlled-release curcumin can manipulate the fate decision of TSPCs, and that it promotes the tenogenesis and inhibits the osteogenesis of TSPCs in a pathological microenvironment, which provides a possible new therapeutic strategy for tendon disease.