Patients with cancer will experience limitations in meeting their daily needs, including psychological problems such as stress. Stress can be assessed through cortisol saliva as a biomarker of stress. Foot Reflexology will help restore the body's energy balance, stimulate relaxation and endorphins, and reduce stress. To determine the effect of foot reflexology to reduce salivary cortisol levels as a biomarker of anxiety for patients with cancer. Adult patients with cancer in stage II and III hospitalized in a Public hospital in Central Java, Indonesia, were invited. Foot reflexology was given once (40 minutes) a day. Saliva collection was carried out two times a day (30 minutes before intervention) and 15 minutes after intervention. Salivary cortisol levels at baseline and post-intervention were measured and compared to determine the effect of foot reflexology. Data were analyzed using the Wilcox on signed-rank and effect size (ES) test. Fifty-five patients (93.2%) participated in this study. We found that the effect size of foot reflexology was 0.82 (ρ = 0.001) with a mean and standard deviation of salivary cortisol levels at baseline and post-intervention were (9.31 ± 5.45 and 6.17 ± 4.55) respectively. These findings indicated the significant effect of giving Foot Reflexology Massage in reducing salivary cortisol levels. Foot Reflexology massage is proven to have a substantial impact on reducing the Salivary cortisol level as a stress biomarker.