This study sought to assess the influence of preschoolers' temperament on their objectively measured physical activity and sedentary time. Actical™ accelerometers were used to measure preschoolers' from London, Canada's (n = 216; 2.5–5 years) physical activity and sedentary levels during childcare hours (5 consecutive days; 15 s epoch). The Child Temperament Questionnaire (CTQ) was used to assess child temperament via parent/guardian report. The six subscales of the CTQ (i.e., reaction to food, soothability, attention span, activity, sociability, and emotionality) were correlated with Actical data (i.e., sedentary time, moderate-to-vigorous physical activity, and total physical activity). The five items of the activity subscale were correlated with these three measures of sedentary time and physical activity. Pearson product–moment correlation coefficients were employed for both sets of analyses. Of the correlations examined, few had an absolute value greater than 0.10, and none were statistically significant after taking multiple comparison bias into account. The results of this work might provide additional indirect support for the conclusion that the childcare environment should be a primary focus with regard to the promotion of increased physical activity and decreased sedentary time among preschoolers. Additional research is required to confirm the relationship between preschoolers' temperament and levels of physical activity and sedentary time.