It is well established that global climate change is currently occurring as a result of human activities and its potential effects has become a focus of recent research. Though there were many reports on plant diseases that cause significant loss in both yield and quality of many crops throughout the world, it is rarely known how disease infection would influence plants under the global climate change. In this study, we investigated the potential impacts of powdery mildew (Podosphaera xanthii) infection on zucchini (Cucurbita pepo) growth under the conditions of elevated CO₂ concentration and rising temperature. Zucchini plants were grown in controlled phytotrons with 3 different simulated climatic conditions: CO₂ 450μmol/mol with temperature ranging from 18 ℃ to 24 ℃ (control treatment), CO₂ 800μmol/mol with temperature ranging from 18 ℃ to 24 ℃ (elevated CO₂ treatment), and CO₂ 800μmol/mol with temperature ranging from 22 ℃ to 28 ℃ (elevated both CO₂ and temperature treatment). P. xanthii was artificially inoculated by spraying a conidial suspension onto the adaxial surface of zucchini leaves. Both physiological (e.g. chlorophyll content, gas exchange activity, and other plant growth parameters) and pathological (e.g. size, hyphal tip number, and conidiophore number of pathogen colony, and disease index of whole plant) responses of plant and pathogen were monitored. The results showed that elevated CO₂ alone enhanced the net photosynthesis rate of zucchini plants (P<0.05), and produced more aboveground biomass and zucchini fruits than those in control treatment (P>0.05). Elevated both CO₂ and temperature also enhanced the net photosynthesis rate but with less enhancement (P<0.05), and greatly accelerated the plant development with more open leaves and male flowers (P<0.05). However, increase of both CO₂ and temperature reduced both chlorophyll content and area of zucchini leaf (P>0.05), finally resulting significantly decreased dry biomass accumulation (aboveground) and zucchini fruit production than the control treatment (P<0.05). No variety on P. xanthii growth and development was found between elevated CO₂ treatment and control treatment, and the plant disease index in elevated CO₂ treatment slightly reduced due to the improved plant resistance caused by increase of atmospheric CO₂. Compared with the control treatment, the fungal development of P. xanthii in elevated both CO₂ and temperature treatment greatly improved, with significantly greater colony size and conidiophore production (P<0.01), as well as much heavier disease index (P<0.01) and much lower yield of zucchini fruits (P<0.01). These results indicate that in future climate characterized by both elevated CO₂ and rising temperature, the powdery mildew would cause aggravated damage on zucchini plants. This finding might be also of importance to disease management on other plants belonging to the family Cucurbitaceae.