Global warming and climate change create an increased demand for the identification of drought and high temperature resistant plants in order to minimalize yield loss in crop plants. Kale (Brassica oleracea var. acephala) is a plant that has shown the ability to grow in high temperature environments and saline soils. In the first part of the experiments 33 varietes of kale from different parts of Croatia and Hercegovina were tested by exposing the seedlings to temperature stress (maximum 38 °C), drought (0,3 M mannitol) and the combination of the two stresses. Root growth, biomass, water and proline content were analyzed and two of the most and least resistant cultivars were chosen for further investigation and comparison. The four kale varieties were exposed to stresses previously described and chlorophyll a fluorescence was measured (OJIP method) as well as hydrogen peroxide content, lipid peroxidation and catalase activity. Levels of HSP70, HSP90 and Rubisco protein were estimated after immunodetection and expression analysis was performed for NAC041 and NAC084 genes. It was found that osmotic stress caused greater morphological changes, greater proline accumulation and more oxidative damage than high temperature stress. The comparison of sensitive and resistant varieties revealed that when exposed to osmotic and high temperature stress, the resistant varieties are able to maintain better photosystem II functionality and performance and had increased levels of HSP70, HSP90 and Rubisco protein. In the sensitive kale cultivar the expression of the NAC041 gene was reduced under osmotic stress and the NAC084 gene under combined high temperature and osmotic stress. The resistant kale cultivar did not show a statistically significant change in NAC041 and NAC084 gene expression between control and stress treatments.