Improving quality of life (QoL) is the goal of behavior analytic services, but there can be barriers to assessing the QoL of autistic children due to characteristics inherent in the condition. Given that happiness is a fundamental element of QoL, previous research has relied on behavioral indicators of mood (e.g., smiling, crying) to evaluate the overall QoL of disabled individuals. However, the use of these traditional indices may not accurately reflect the emotional well-being of autistic individuals, who are known to engage in idiosyncratic mood indicators. The current study replicated selected procedures from Parsons et al. (2012) to identify and validate the unique mood indicators of young autistic children. The study showed that individualized indices of happiness and unhappiness could be operationally defined and reliably measured among these children. Key findings and limitations of this study are discussed, and the implications of these findings are presented.