Introduction: Evaluating service quality and satisfaction is central to the provision of accessible and developmentally appropriate youth mental health services. However, there are limited suitable measures and a lack of published evidence on the psychometric properties of measures to assess young people's satisfaction with youth mental health services. The headspace Youth (Mental Health) Service Satisfaction Scale (YSSS) was designed and implemented to assess young people's satisfaction with headspace mental health services in Australia. This study examined the reliability and factor structure of the YSSS in a youth mental health service in Ireland. Methods: The sample comprised 1449 young people (66.2% female) aged 12–25 years (M = 16.48, SD = 2.97). Participants completed the YSSS after their final brief intervention session through Jigsaw—The National Centre for Youth Mental Health. Confirmatory factor analysis (CFA) was performed on one- and four-factor models to test findings from previous studies. Reliability was also examined. Results: CFA supported a single-factor structure of the YSSS, and all items were suitable for inclusion. The internal consistency of the measure was deemed acceptable (α = 0.89). Conclusions: Findings suggest that the YSSS is a reliable measure for monitoring satisfaction with youth mental health services in an Irish context. The measure demonstrated a unidimensional construct of satisfaction. These findings support the broader application of the YSSS and add to existing knowledge on measuring satisfaction within youth mental health services.