Global warming has indisputably caused climate change, which is probably the largest threat to existing forest ecosystems in Europe. Given the ecological and economic importance of beech in Europe and Croatia, the aim of this study was to determine the impact of changed climatic conditions on crown defoliation and nutrition of beech, as well as the relationship between these two vitality indicators. The research was conducted on 28 research plots that are part of the UNECE ICP Forests infrastructure in Croatia. The impact of climate on defoliation was studied on the basis of defoliation data collected as part of the program for monitoring the damage of forest ecosystems in Croatia in the period from 1996 to 2017. Data were calculated as the defoliation in the current year, as well as the difference compared to the previous year (defoliation change). The assessment was performed on the same plots in the period 2018 - 2020 in order to determine the trees for sampling of plant material (leaves). Samples of beech leaves for the analysis of nutrient concentrations were collected once a year in the period from 2018 to 2020, separately for trees up to 25 % and above 25 % of defoliation. The defoliation of beech trees shows a significant positive trend on which drought has a significant, although weak impact. The lack of a clear trend of defoliation change as well as the pronounced impact of drought in the previous year indicates that defoliation change is a reflection of intense stress, while the positive trend of defoliation shows the accumulated impact of location-specific stressful environmental conditions on tree vitality. The results of this research provides the first insight into the nutritional status of beech at the level of the whole of Croatia and indicate a satisfactory beech nutrition in comparison with limit values. The study of the relationship between defoliation and nutrition did not determine the relationships between the defoliation categoryand nutrition of beech trees. Significant differences were observed in the concentrations of P, Ca and Mg in relation to defoliation, but which are valid only for individual years. Precipitation has a positive effect on N and K concentrations. An increase in SPEI results in higher Mg concentrations and reduced Ca and N concentrations, while an increase in SPEI in the previous year causes increased N, P and K concentrations. Positive temperature deviations from climatic normal affect P, K and Ca concentrations, whi increasing average annual temperature increases the concentration of N.