The goal of the present study was to develop a stress paradigm to elicit cortisol secretory responses in a group of 5- and 6-year-old children as a whole. To this end, we tested a paradigm containing elements of social evaluative threat, unpredictability and uncontrollability, and with a duration of 20 min. The Children's Reactions to Evaluation Stress Test is composed of three short tasks that children have to perform in front of a judge. The tasks are rigged so as to provoke (partial) failure in the child's performance. Participants were 42 children (M = 68.0 months, SD = 4.3). Six saliva samples were taken during the testing session to obtain cortisol measurements of baseline concentrations, stress reactivity, and recovery. Our findings showed that this paradigm was effective in provoking a significant increase in salivary cortisol concentration in the group as a whole, with no effects of possible confounders (child's sex, age or school, parental educational level, time of testing, sex of experimenter, and sex of judge). The mean cortisol concentration increase for the group was 127.5% (SD = 190.9); 61% of the children could be classified as reactors (mean increase of 214%, SD = 201.5), and 39% as non-reactors (mean decrease of 7.8%, SD = 16.8). To our knowledge, this is the first study in this age group that shows a significant cortisol response for the group as a whole to a standardized laboratory paradigm. As such, this paradigm is a promising tool to be used in future research on early life interactions between physiology and psychology.