Objective: The aim of the present study was to investigate the influence of formative feedback for the coach on the agreement between intended, observed and perceived exertion in soccer. Methods: A quasi-experimental study design was conducted using a feedback intervention. Agreement between coach and players was assessed with and without feedback. The coach filled in the Rating of Intended Exertion (RIE) before training and the Rating of Observed Exertion (ROE) after the training for all individual players. Twelve U23 (age 20.3 ± 1.5; height 180.5 ± 4.8 cm; weight 74.8 ± 6.6 kg) soccer players registered Rate of Perceived Exertion (RPE). Furthermore, training duration (minutes), total distance (km), average speed (km·h−1), number of sprints, distance >14.4 km·h−1 (km), TRIMP and time >85% maximal heart rate (min) were collected. Results: About 231 RPEs were collected and paired with RIE and ROE of the coach. The average discrepancy between ROE and RPE, decreased from 1.0 ± 0.89 without feedback to 0.7 ± 0.73 with feedback (p < 0.003, ES 0.4). Further analyses revealed that this reduction in mismatch was particularly present in hard training sessions (p < 0.004, ES 0.6), but not for easy and intermediate sessions. The mismatch between RIE and RPE did not improve. Conclusions: The results indicate that feedback improves the ability of a soccer coach to observe individual player exertion for most players, with small to moderate effect sizes. The mismatch between intended and perceived exertion did not improve with feedback. The use of formative feedback about load to coaches is recommended, particularly after hard sessions.