The Five-factor theory of personality (FFT) has pervaded personality research in recent years. Although many reliable and valid measurement instruments exist for use with adults, adolescents, and even elementary-age children, there is a lack of available 5-factor measurement tools for use with preschool children. This article expands on previous work developing the M5-PS, a rating form for preschool children designed to be completed by classroom teachers or caregivers. A total of 621 children were rated by their teachers on the 90-item working form of the M5-PS. Through a combination of empirical and rational scale refinement methods, the number of items has been reduced to 35, yielding a revised instrument, the M5-PS-35, with substantially improved construct validity and scale internal consistency. Potential changes in external validity were evaluated by comparative reanalysis of an existing data set.