This study attempts to examine and identify instances of negative “interlanguage transfer” (Sharwood Smith & Kellerman, 1986), which is a phenomenon belonging to the broader field of crosslinguistic influence, in written L3 English production in a bilingual Italian/German population. Transfer from learners’ L2 has attracted increasing attention over recent years (De Angelis & Selinker, 2001; Jessner, 2006) and research has suggested various potential triggers for facilitative and negative L2 transfer, as well as producing mixed results regarding the individual aspects of language that may be susceptible to transfer from a learner’s L2. Quantitative data were collected from 46 subjects in the form of questionnaires enquiring about language backgrounds and attitudes, and written summaries. The Statistical Package for Social Science was used to analyse specific instances of written syntactic errors resulting from both L1 and L2 transfer and these were then examined in the light of the questionnaire responses in order to identify possible determining factors behind any L2 transfer for both linguistic groups. Results provided evidence of negative syntactic L2 transfer from German and Italian in English L3, yet the possible determining factors were sometimes unexpected and not necessarily identical for both groups. This study suggests that L2 transfer in multilingual settings is a very real possibility which may be of future interest in terms of multilingual language processing and have consequences for the L3 classroom.