The framework of our research work is the GPR Bordeaux Plant Sciences (WP PHYTOSTIM). Our focus lies in investigating plant stimulation using biostimulants, to tackle environmental stresses and investigate underlying physiological and metabolic tradeoffs. Tomato (Solanum lycopersicum L.) is an important horticultural crop, typically cultivated during the summer months, aiming for a commercial maturity from July, in Europe. However, with the escalating frequency and intensity of high temperatures due to climate change, greenhouse tomato culture faces the challenge of navigating through heatwave periods, particularly during the reproductive stage. Our study aims to evaluate the impact of a biostimulant application on tomato metabolism, with or without thermic stress, at the beginning of the summer. Over two cultivation periods (2021 and 2022), employing a biostimulant derived from seaweed extract (Ascophyllum nodosum, L., Stim Pure liquid, Van Iparen), we gathered phenotypic observations and tomato samples from three organ types (Apex Leaf, Fully Expanded Leaf, and pericarp). Additionally, we performed targeted and non-targeted high-throughput analytical strategies by enzymatic measurements, and Liquid Chromatography coupled to tandem Mass Spectrometry on the leaf and fruit samples. Fruit yield is the variable that reflects crop performance. The results showed the effect of the condition of application (ferti-irrigation or rootball soaking at potting time). The fruit and leaf metabolome allowed discriminating between different biostimulant application methods and the control (treatment with water). The perspective of this work is to predict the performance of tomato crop and to gain highlight on molecular, metabolic, cellular and physiological mechanisms, underlying biostimulant efficacy.