LAY ABSTRACT: Parental Expressed Emotion refers to the intensity and nature of emotion shown when a parent talks about their child, and has been linked to child behaviour outcomes. Parental Expressed Emotion has typically been measured using the Five-Minute Speech Sample; however, the Autism-Specific Five-Minute Speech Sample was developed to better capture Expressed Emotion for parents of children on the autism spectrum. In each case, parents are asked to talk for 5 min about their child and how they get along with their child. Parents' statements are then coded for features such as number of positive and critical comments, or statements reflecting strong emotional involvement. While both the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample have been used with parents of autistic school-aged children, their relative usefulness for measuring Expressed Emotion in parents of preschool-aged children - including their links to child behaviour problems in this group - is unclear. We collected speech samples from 51 parents of newly diagnosed autistic preschoolers to investigate similarities and differences in results from the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample coding schemes. This included exploring the extent to which the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample, separately, or together, predicted current and future child behaviour problems. While the two measures were related, we found only the Autism-Specific Five-Minute Speech Sample - but not the Five-Minute Speech Sample - was related to child behavioural challenges. This adds support to the suggestion that the Autism-Specific Five-Minute Speech Sample may be a more useful measure of parental Expressed Emotion in this group, and provides a first step towards understanding how autistic children might be better supported by targeting parental Expressed Emotion.