Neck and shoulder stiffness is a typical subjective symptom in developed countries. This stiffness is caused by factors such as muscle tension and poor blood flow, leading to reduce work efficiency and diminish QOL. NKCP^®, a natto -derived dietary food supplement whose main component is bacillopeptidase F, has antithrombotic, fibrinolytic, and blood viscosity-lowering effects. Here, we investigated the effect of NKCP^® on neck and shoulder stiffness in a double-blind placebo-controlled randomized crossover study. Thirty subjects with neck and shoulder stiffness were randomly divided into 2 groups and ingested 250 mg of NKCP^® or placebo daily for 4 weeks. Headache score significantly improved in the NKCP^® group compared to the placebo group. Moreover, NKCP^® significantly improved the score of visual analogue scale for neck and shoulder stiffness and pain, reduced muscle stiffness of the neck, and increased the skin surface temperature of neck and shoulders, compared to before ingestion. No adverse effects were observed during this study. These results suggest that NKCP^® may alleviate headaches and chronic neck and shoulder stiffness and pain.