The major fiber crop cotton (Gossypium hirsutum L.) holds worldwide economic value yet its production faces increasing threats from the temperature rises caused by climate change. Heat stress, particularly during the reproductive phase, impairs floral development, boll retention, and fiber elongation, resulting in yield and quality losses. This study aimed to identify heat-tolerant upland cotton genotypes through the combined evaluation of morphological and physiological traits under field conditions reflecting regional thermal extremes. The experiment was conducted at the Cotton Research Station, Faisalabad, under both optimal and elevated temperature regimes. Significant genotypic variation was observed in yield-related parameters, including boll retention, number of bolls per plant, seed cotton yield, and plant height. High temperature reduced photosystem II efficiency and relative water content, while tolerant genotypes maintained higher chlorophyll stability, photosynthetic rate, and overall plant vigor. The results indicate that sustained photosynthetic efficiency and water balance under heat stress are key factors contributing to thermotolerance. Future studies involving biochemical assays, such as antioxidant enzyme activity and osmolyte accumulation, will be undertaken to validate the physiological basis of heat tolerance further and improve screening accuracy for resilient cotton cultivars. Hence, integrated approach is expected to provide reliable basis for selection of heat resilient cotton genotypes.