This study investigates the interplay between online and face-to-face (FtF) feedback on stress during an important life event. We present data on a two-month, six-wave longitudinal study of 468 Chilean adolescents across three important stages of a competitive national university selection test (Prueba de Seleccion Universitaria [PSU]) to assess longitudinal and reciprocal relationships. Random intercept cross-lagged panel models (RI-CLPM) showed that online feedback had a small effect in decreasing stress during the three short-termed waves, before and after the three main events of the test: test taking, test scores, and final selection. No intrapersonal effects were found for FtF feedback on stress, and vice versa. At the interpersonal level, only feedback variables were related. Results suggest that prosocial replies on social media may slightly help to downregulate stress from important life events at the intrapersonal level, an effect which appears to be short-lived (e.g., only a few days), rather than long-lived (e.g., three weeks).