Place the dijon mustard, honey, olive oil, balsamic vinegar, garlic, salt, and pepper in a glass jar and shake or stir until fully combined.
Add half the marinade and the chicken tenders to a large ziploc bag. Shake to fully coat the chicken and marinate for at least 1 hour, or up to 10 hours.
Heat a griddled cast iron pan on medium heat. When hot, add the chicken and cook for 3-4 minutes on each side until chicken is browned and internal temperature has reached 165° F.