<p>Effective use of virtual simulations in the science classroom improves comprehension of concepts and models, increases motivation, and promotes acquisition of scientific competences. Despite these benefits, their use in secondary teaching is not widespread. This work analyses the factors that influence use of virtual simulations by science teachers in secondary education. To do this, a mixed study with 609 STEM teachers was performed. The results showed limited use of virtual simulations, significant demand for training in them, and three principal problems that hinder their use: logistics in schools; availability of simulations; and teachers’ time constraints and need for training in how to use them. Accordingly, there is a need to implement educational policies and training programmes that take into account teachers’ problems in searching for simulations and integrating them in the classroom.</p>