This paper investigates binaural beat stimulation (BBs) on mitigating mental stress levels at the workplace. We developed an experimental protocol to induce stress levels by performing Stroop Color-Word Task (SCWT) under time pressure and negative feedback. Then, we mitigated the levels of stress using 16 Hz BBs. The level of stress was assessed by utilizing Functional Near-Infrared Spectroscopy (fNIRS), salivary alpha-amylase, and behavioral responses. We quantified the level of stress using statistical analysis, functional connectivity based on Phase Locking Value (PLV), and support vector machines (SVM) classifier. We found that BBs has significantly improved the accuracy of target detection by 27.35 %, (p<0.005) and reduced the cortisol level. The classification results showed that the SVM technique with PLV features differentiates between three levels of mental states (control, stress and mitigation) with an average accuracy of 65.22%, and sensitivity of 81.79% and specificity of 80.10%.