Background <p>Routine effective tooth brushing with fluoridated toothpaste has a substantial impact on preventing dental caries. Parent and child roles in establishing routine tooth brushing habits in preschool children encounter numerous challenges. The Malay version of the Parenting and Child Tooth Brushing Assessment (M-PACTA) is a comprehensive tool with four scales that assesses various aspects of parent-child behaviour during tooth brushing. However, it lacks a clear threshold score for each scale to distinguish between favourable and unfavourable outcomes. Therefore, it is imperative to develop a reliable cutoff score for each scale of the M-PACTA.</p> Objective <p>This study aimed to determine the minimum cutoff score for child’s behaviour, parental strategies, attitude, and knowledge scales of the M-PACTA using the modified Angoff method.</p> Methods <p>A panel of nine experts, including paediatric and community dental specialists, independently assessed 77 items in M-PACTA. The experts were required to indicate good and bad outcomes of each item of the M-PACTA. Cronbach’s alpha was used to evaluate inter-rater agreement, and the final scores for each scale were determined by summing up the mean score for each item.</p> Results <p>The cutoff scores for child behaviour, parental strategies, attitude, and knowledge scales was determined to be 37, 98, 44, and 41, respectively. The interrater agreement yielded a Cronbach’s alpha of 0.958.</p> Conclusions <p>In conclusion, the cutoff score for each scale in the M-PACTA questionnaire- child’s behaviour, parental strategy, attitude, and knowledge was determined for the Malaysian population.</p>