This study investigated the physiological and biochemical responses of three sunflower (Helianthus annuus L.) hybrids (Luka, Matej, and OS-H-17) under field conditions in 2021 and 2022. According to the analysed data, significant year variability was observed. In 2021, higher ambient and leaf temperatures, as well as higher radiation, led to reduced performance index (PIABS) and increased phenolic accumulation. In 2022, slightly cooler conditions with lower radiation favoured higher chlorophyll content, PIABS, and higher catalase and ascorbate peroxidase activities. Principal component analysis separated years and differentiated hybrids according to their response strategies. Luka was associated with chlorophyll stability and enzymatic antioxidants, while Matej and OS-H-17 relied more on non-enzymatic mechanisms. Therefore, variations in the environment have a significant effect on the physiology and biochemical responses of sunflowers. Hybrids have exhibited specific characteristics related to adaptive mechanisms. Luka showed the most stable antioxidant and photosynthetic performance, highlighting the importance of hybrid selection in producing climate-resistant sunflowers.