Increasingly high temperatures are one of the challenges of climate change, which in turn negatively affects the production of horticultural crops. Additionally, heat stress severely reduces agricultural yield worldwide and is one of the main factors restricting plant development. Heat stress can be overcome by using some antioxidants, which have a role in stimulating growth and fruit setting. Two field experiments were carried out during the two successive late summer seasons of 2022 and 2023 in loamy clay soil to study the response of tomato plants cv. F₁ Hybrid K-186 for melatonin, 6-benzylaminopurine, anise oil, jasmonic acid, eugenol, potassium silicate, and control (only water tap) on vegetative growth, fruit set, yield, fruit characters, and some chemical components of tomato plants grown under high temperature conditions. Our results revealed that the treatments of melatonin, 6- benzylaminopurine and potassium silicate had significant increase in early and total yield of tomato plants as well as yield attributes at heat stress in the open field. Spraying of melatonin treatment led to an increase the total yield by 39.65% in the average of the two seasons. Accordingly, it can be recommended that applied melatonin or used 6-benzylaminopurine treatments to improve tomato yield productivity under heat stress conditions in the open field.