Trees usually face simultaneous stresses and have evolved to deal with them naturally. However, as a consequence of climate change, heat waves and drought stress have become more intense, frequent, and long-lasting than the adaptative capacity of trees. How trees can cope with stress and acclimate will benefit our forest management and genetic improvement programs aimed to maintain forest sustainability. Maritime pine has a remarkable adaptive capacity, based on its metabolic plasticity, which allows this specie to grow in a wide range of climatic conditions. Consequently, this work aims to investigate P. pinaster metabolome in response to different intensities of combined stresses. To assess the acclimation gradual changes to heat and drought stress, we established a five-time-point experiment simulating a seven-day heat wave (temperature reaches 30 ºC and 40 ºC) accompanied by different water availability. Low-intensity stresses (30 ºC and low water stress) provoked metabolic acclimation accumulating those compounds necessary if the environmental conditions worsen and stress intensity increases. The main pathways involved were amino acid and carbohydrate metabolism leading to an enhanced accumulation of phenolics, flavonoids, and terpenoids. When plantlets were exposed to high-intensity stress (40 ºC and high water stress), secondary metabolism took a prominent role, through alkaloids, lignans, and glycosyloxyflavones. Overall, this work provides new insights into the metabolic mechanisms under both stresses and pointed out the need to combine stresses and intensities, as plant responses are not predictable from the study of isolated stresses. © 2023 The Authors