Multilingualism has recently come to the forefront of language education in Europe.Research on multilingualism has focused mainly on how third or additional languages (L3s) are learnt, how they should be taught, and what the profile of the L3 teacher should be.However, L3 programmes and teacher training courses do not seem to have echoed these findings yet.This study sets out to investigate the current mismatch between how L3s are being learnt (i.e., as L3s) and how they are being taught (i.e., as second languages or L2s). Based on the premise that teachers' beliefs are the strongest predictors of teachers' practices, this study aims to assess the beliefs that L3 teachers in Europe hold about multilingualism (i.e., about L3 learning, L3 teaching and the L3 teacher). In order to suggest measures which could help reduce the current mismatch, this study also aims to identify any background variables which may be associated with differences in these beliefs.Data was collected through an online questionnaire which received responses from 984 teachers of Spanish, French and German, the three most popular L3s in Europe (European Commission, 2012a, 2012b, working in 34 European countries. Results confirm the mismatch identified at the beginning, with L3 teachers showing only partial awareness of how L3 learning, L3 teaching and the profile of the L3 teacher differ from those in L2 education. The results also suggest that teachers who are more multilingual, have formal qualifications in other languages, and have experience teaching languages other than the L3 generally have more accurate beliefs about multilingualism.In light of these results, training programmes and recruitment policies should be reconsidered to ensure that active and prospective L3 teachers have more adequate beliefs about multilingualism. In turn, this will lead to L3 teaching practices that are more suitable to address the needs of L3 learners, helping reduce the extent of the current mismatch.