In recent years there has been a growing recognition by the Government that to raise academic attainment requires a more holistic view of children's needs (DfES, 2003b, DfES 2005a; 2005b). This realisation has led to a number of Government initiatives focusing on the importance of emotional literacy (El) in education (Children Act 2004; DfES, 2003b; DfES 2005a; 2005b; NHS & DCSF, 2007). In the context of the foregoing, this mixed methods research evaluated an intervention taking place in a local Authority (LA) in north-east England aimed at developing children's emotional wellbeing, the Emotional Literacy Support Assistant (ELSA) project. The evaluation focused on the impact of an ELSA project on support assistants' self-efficacy for working with children and children's emotional selfefficacy beliefs. Originality was achieved as the former concept had not been investigated before and previous research into the latter concept was limited to the USA (Suldo & Shaffer, 2007) and Netherlands (Muris, 2001). The impact of the ELSA project on support assistants' self-efficacy for working with children and children's emotional self-efficacy was examined using a cross sectional investigation. A pre-post control group investigation was also used to further investigate the impact of the ELSA project on support assistants' selfefficacy for working with children. Measures of the aforementioned concepts did not exist in the literature. Therefore, through facilitating focus groups with the ElSAs and children to explore their constructs of the concepts, this study developed two new and highly consistent questionnaires. It was hypothesised that support assistants' self-efficacy beliefs for working with children would increase post ELSA training and that they would be higher than those of non-ELSA trained support assistants. It was also hypothesised that the emotional self-efficacy beliefs of children who had received ELSA support would be higher than those of children who had not received ELSA support. Both the quantitative and qualitative results supported the hypotheses and the ELSA project was found to have a positive impact on support assistants' and children's selfefficacy beliefs. Support assistants which were found to have the greatest impact on children's emotional self-efficacy beliefs had: completed the ELSA training, protected time to plan their ELSA work and protected time to attend refresher training events. The implications of these findings for future research, Educational Psychologists and educational practice are considered.