Technology acceptance model (TAM) is one of the models that is used to explain the acceptance and use of technology with user perceptions and attitudes. Some researchers argued that TAM should include external variables, such as subjective norms, to improve our understanding of the effect of social impact on technology acceptance. The purpose of this study was to investigate the effect of subjective norms on preservice and in-service teachers' perceptions, attitudes and behavioural intention to use technology in Turkey. We adopted a multigroup confirmatory factor analysis method to establish measurement invariance across the groups and to investigate the relationships in the research model. The sample consisted of 324 preservice and 517 in-service teachers. Results revealed that attitude towards computer use was the most dominant predictor of behavioural intention in both preservice and in-service teachers. Subjective norms had a large total effect on behavioural intention in preservice teachers; however, the same effect was smaller in in-service teachers. Moreover, subjective norms played an important role in forming an attitude towards technology use in preservice teachers. On the other hand, in-service teachers considered the usefulness of technology in forming a positive attitude. We discussed the implications of the findings for both theory and practice. Practitioner Notes What is already known about the topic Technology acceptance model (TAM) is one of the most widely used models in technology acceptance and use. Acceptance and use of technology by preservice and in-service teachers are important for an effective integration process in educational settings. Social factors such as subjective norms impact technology acceptance and use behaviours of individuals. What this paper adds An extended TAM helps explain the technology acceptance and use behaviours of preservice and in-service teachers. Attitude towards computer use is a good predictor of both preservice and in-service teachers' behavioural intention to use technology. Preservice and in-service teachers' behavioural intention to use technology is affected by subjective norms. Subjective norms' effect on forming an attitude towards computer use is greater in preservice teachers than it is in in-service teachers. Implications for practice and/or policy In teacher education programmes, instructors and administrators should require students to use technology in class activities and assignments and during internship practices to increase the possibility of students' use of technology in their professional life. At schools, administrators and supervisors should mandate teachers to use technology that is easy to use in their classes, but they should also show teachers how technology can benefit their instructional practices. Instructional designers and IT developers should consider the affordances offered by ICT and provide teachers with quality, effective and easily administered user manuals or job aids.