Introduction: Fundamental movement skills (FMS) are goal directed movement patterns. They are seen as a pre-requisite for the development of sport specific skills, and are a contributor towards future participation in sport and physical activity (PA). A lack of confidence and ability in performing these skills may lead to withdrawal from participating in PA, creating a vicious circle that can result in the reduction of the necessary practice of these FMS. The Youth-Physical Activity Towards Health (Y-PATH) intervention was developed and implemented with the aim of improving adolescents FMS proficiency levels and attitudes towards PA participation, with an overall goal of increasing PA levels. Methods: Participants (n = 564, 12-14 years of age) from 20 mixed gender post- primary schools were recruited as part of the Y-PATH cluster randomised controlled trial. A total of 15 FMS were assessed using a combination of process oriented measures including the TGMD-2. Participants’ PA levels, BMI, fitness levels and physical self-confidence levels were also assessed pre-intervention at the start of the school year. Post-intervention testing was completed at the end of the school year, and again three months later to assess any retention of changes which occurred. The reliability and validity of the physical self-confidence scale and TMGD-2 used in this study were also assessed. Results: Results indicate that Irish adolescent youth are performing below the expected FMS proficiency levels for their age group. Males are significantly more proficient than females in both overall FMS (p=0.02) and object control scores (p=0.001). Results of a between groups ANOVA indicate that the intervention group improved by significantly more than the control group over the period of the intervention (p<0.001). Males exhibited significantly higher physical self-confidence scores than females (p<0.001). A significant correlation was found between females FMS score and their physical self-confidence (r=0.305, p<0.001), while there was no correlation between these two variables among males (r=0.101, p=0.209). Results indicate that the physical self-confidence scale is a valid (r=0.72) and reliable (r=0.92) tool for use with adolescents. A 2 factor model with a reduction in the number of skills in the TGMD-2 to just seven (run, gallop, hop, horizontal jump, bounce, kick and roll) revealed an overall good fit for use with adolescents. Conclusion: The results of this study highlight that Y-PATH is an effective intervention to improve adolescents FMS proficiency. To further improve FMS and PA levels interventions should be implemented and assessed longitudinally and physical self-confidence should be monitored and improved accordingly as it is said to provoke behavioural change.