Lifelong learning is a key element in the quality of teaching at any level, so in Secondary Education too. Teachers often feel unprepared to teach and need ongoing training. This training does not always take place within a formal framework, but increasingly involves non-formal and informal aspects. In order to better understand the way they learn, the concept of Learning Ecologies (From now on, LE) is used as a starting point in this research and our main objective is to analyze the LE of practicing secondary school teachers, focusing on the influence of the use of ICT. A qualitative methodology was used with a semi-structured interview as an instrument to collect information from 12 teachers selected using previous criteria (a case study design). We have used Nvivo to analyze data and we have used four dimensions of analysis: learning, tools, benefits, and disadvantages. It was found that informal learning has a main role in the in-service training of secondary school teachers and to carry out this training, they use tools such as Twitter, Facebook, or WhatsApp. The main benefit of using ICT for their training is ubiquity and flexibility. Some teachers indicate that the amount of existing information is one of the main disadvantages. Overall, it is concluded that ICT are considered a great resource for teachers within their LE and for their professional development.