Many autistic children have co-occurring behavioural problems influencing core autism symptomology potentially relevant for intervention planning. Parental Expressed Emotion – reflecting critical, hostile and overprotective comments – contributes to understanding and predicting behaviour in autistic school-aged children, adolescents and adults and is typically measured using the Five-Minute Speech Sample. However, limitations exist for its use with parents of younger autistic children and so the Autism-Specific Five-Minute Speech Sample was adapted with the goal of better measuring parent Expressed Emotion in the context of childhood autism. The Autism-Specific Five-Minute Speech Sample has not yet been used to explore Expressed Emotion in parents of autistic preschoolers, nor has the relative predictive utility of the Autism-Specific Five-Minute Speech Sample and Five-Minute Speech Sample been evaluated in the same sample. We compared the two measures from speech samples provided by 51 Australian parents with newly diagnosed autistic preschoolers, including investigating their predictive value for concurrent and subsequent child internalising and externalising behaviour problems. While Autism-Specific Five-Minute Speech Sample Expressed Emotion and Five-Minute Speech Sample Expressed Emotion were associated in this sample, only Autism-Specific Five-Minute Speech Sample codes contributed significant predictive value for concurrent and subsequent child problem behaviour. These preliminary data strengthen the position that the Autism-Specific Five-Minute Speech Sample may better capture Expressed Emotion, than the Five-Minute Speech Sample, among parents of autistic preschool-aged children. 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.