Schools are increasingly encouraged to adopt evidence-based or evidence informed interventions and implement them using insights from implementation science. The literature relating to implementation of interventions in schools has focused largely on universal interventions, particularly for social and emotional learning (SEL), which are designed for all children and young people. In contrast, targeted interventions provide additional support for those pupils who may require small group or individual support over and above that provided at the universal level. To date there has been limited consideration of factors which are important for the implementation of targeted SEL interventions. Data from an exploratory case study with two schools implementing Lego therapy are used to illustrate the implementation factors relevant to this targeted intervention. Findings indicate similarities in universal and targeted intervention core components and factors but also a number of distinct elements that are important to consider when implementing Lego therapy and potentially other targeted SEL interventions. Key considerations include the interaction with the wider school system, the pivotal role of the intervention champion, and the importance of external support for problem solving and sustainability. The resulting model may inform further development of implementation frameworks for Lego therapy and other targeted SEL interventions.