The purpose of this experiment was to determine whether the open feedback system used in synchronized swimming (i.e., the judges hear and see each others’ scores after having rated each performance) leads to unwanted (i.e., nonperformance-based) conformity in the scoring by judges. Twenty judges in synchronized swimming were randomly divided into four panels of five judges. They had to rate 60 performances of the same imposed figure, the barracuda twirl: 30 performances in Phase 1 and 30 in Phase 2. Two independent variables were orthogonally manipulated: feedback (or none) during Phase 1 and feedback (or none) during Phase 2. In line with the hypotheses, the variation of scores given in Phase 1 was significantly smaller when the judges had received feedback than when they had not received feedback. Moreover, the variation of the scores given in Phase 2 remained significantly smaller among the judges who had received feedback in Phase 1 but not in Phase 2, compared with judges who had not received feedback in either phase. These results indicate that the scoring of judges in synchronized swimming is strongly and lastingly influenced by immediate feedback.