Evaluative conditioning (EC) refers to a change in liking of a conditioned stimulus (CS) consecutive to its repeated pairing with a valent unconditioned stimulus (US). We relied on a multinomial processing tree model to compare the processes underlying EC in middle-aged children (n = 57; Mage = 8.65; range = 6.94—11.03; 31 females) and young adults (n = 57; Mage = 19.16; range = 17.60—23.60; 53 females). We found that controllable and uncontrollable valence transfer processes concurrently contributed to EC in adults and provided initial evidence that they are already present in children. Moreover, the experiment revealed that both types of processes are weaker in children than in adults and that controllable processes are stronger in older children than in younger ones. These findings suggest that both controllable and uncontrollable processes already underlie EC in middle-aged children but that they continue to mature after childhood.