The increasing use of digital resources has changed the way of teaching, where platforms such as YouTube offer large repositories of educational videos. There are many theoretical studies that analyse the digital competences of teachers, but to a lesser extent on the behaviours and use that the teacher makes of this multimedia platform. Thus, the purpose of this study is the development of an instrument in which it is analysed how the behavioural intention of teachers on YouTube impacts their digital competence to search and select information, share information, and interact with other users of the platform, and create educational material. To achieve this, following the partial least squares (PLS) method of structural equation models, a higher-order causal model was proposed based on an adaptation and extension of the Unified Theory of Acceptance and Use of Technology (UTAUT). The study was carried out with a sample of 2157 teachers from all over Spain. The main result was that behavioural intention explained 22.70% of the true variance of teachers' digital competence. In addition, it has been possible to verify the reliability, convergent and discriminant validity of the established causal relationships, determining a model with acceptable goodness-of-fit. These findings show that it is a valid and reliable instrument to measure teachers' digital competences on YouTube, behavioural intention, and the system of relationships between factors.