Agricultural rivers are highly affected by metal pollution, with copper being frequently detected. However, the pollution of surface waters must be viewed in a context of global change, and aquatic systems are generally subjected to multi-stress conditions, due to multiple chemical and/or physical pressures. Among the various environmental factors, a special attention should be paid to climatic changes, which can lead to rising temperatures. In lotic ecosystems, periphytic biofilms assume key ecological functions such as primary production and nutrient cycling. Indeed, even if effects of metals on microbial communities are relatively well known, there is a lack of data about the possible interactions between temperature increase and metal pollution. Accordingly, the present study aimed to evaluate in microcosms the influence of temperature increase on the response of biofilms to copper exposure (about 20 µg L-1). Winter communities, collected in a 8°C water, were subjected for six weeks to four thermal conditions in presence or not of copper. At the initial river temperature (8°C), our results confirmed the chronic impact of copper on biofilms, both in terms of structure (biomass, distribution of algal groups, diatomic composition) and function (photosynthetic potential) throughout the study. At higher temperatures (13, 18 and 23°C), the effects were transient and varied according to the measured parameters. Statistical analysis revealed a significant interaction between temperature and copper. Furthermore, our study seemed to suggest that temperature can modify Cu bioavaibility. It is necessary to study these interactions in order to better understand the ecotoxicological impact of metals in multi-stressed environments.