Effective mentoring of preservice EFL teachers may advance EFL teaching practices. Five factors for mentoring have been identified, namely, Personal Attributes, System Requirements, Pedagogical Knowledge, Modelling, and Feedback. An empirically-based survey instrument focused on 106 Vietnamese preservice teachers’ perceptions of their mentoring for EFL teaching across these five factors. Apart from acceptable Cronbach alpha scores for four of the five factors, (System Requirements was .08 below the accepted .70 level), analysis revealed that more than 50% of these preservice teachers perceived they had not received mentoring for developing their teaching of English writing on 29 of the 34 survey items. The mentoring instrument can be used to gauge mentoring practices and attributes for identifying mentors’ professional development needs towards enhancing such practices