<p>High temperatures disrupt physiological processes and canopy microclimate, making sunburn a major constraint to Daisy mandarin in arid regions by disturbing biochemical homeostasis and reducing fruit quality and yield. The present study evaluated kaolin (2%, 4%, 6%) and salicylic acid (300 ppm) to enhance physiological resilience and biochemical defense responses of Daisy mandarin in Punjab, India during 2024 under irrigated arid conditions. Combined application of 6% kaolin with salicylic acid significantly reduced sunburn incidence by lowering fruit, leaf, and inner canopy temperature demonstrating its role in thermal shielding and microclimate regulation. Heat stress in untreated plants triggered elevated proline accumulation and flavonoid levels alongside anatomical injury such as reduced intercellular spaces in peel tissue. In contrast, treated plants showed moderated proline accumulation and improved antioxidant status through higher phenolics, carotenoids, and chlorophyll content, reflecting enhanced redox balance and sustained photosynthetic function. Combined application of 6% kaolin with salicylic acid significantly improved fruit firmness, peel thickness, colour development, and fruit yield. Fruit quality indices such as sugars, total soluble solids, acidity balance, and vitamin C also improved under treatment. These observations indicate that combined application of kaolin and salicylic acid could be a viable strategy to mitigate heat and radiation stress and sunburn in Daisy mandarin by activating both biochemical stress alleviation pathways and physiological cooling strategies.</p>