ABSTRACT Creativity evaluation, particularly rating the creativity of products, is an unstable construct subjective to the influence of various individual states and characteristics. However, little research has been conducted on whether and how participants’ physiological states affect rating products. This experimental study aimed to explore how synchrony (i.e. whether individuals’ evaluation time synchronizes with their peak circadian arousal periods during a day) affects the rating of creativity in drawings, whether these effects vary according to drawings’ different creativity levels, and the influence of emotional state on synchrony and creativity rating. A sample of 191 university students rated several drawings of low, medium, and high creativity levels at their optimal or non-optimal times of day, and their subjective emotional valence and arousal were recorded. The results showed that participants exhibited a more positive rater bias when rating low- and medium-creativity-level drawings during their optimal times of day. Emotional arousal, but not valence, mediated the relationship between synchrony and rater bias. These findings highlight the role of synchrony and emotional arousal in rating creative products, contributing to our understanding of how raters’ synchrony states influence creativity evaluation.