This study investigates the vocabulary knowledge, beliefs, and practices of adult English as a second language (ESL) instructors. Thirty participants responded to an online survey designed to elicit information regarding their knowledge and beliefs; approaches to assessment; vocabulary teaching techniques and strategies; instructional practices related to repetition, retention, and extensive reading; use of technology, dictionaries, frequency lists, corpora, and formulaic sequences; and professional development interests. We used descriptive statistics to analyze responses and identified discrepancies between teacher beliefs/practices and current research findings in: (1) the setting of instructional priorities (word phrase frequency and coverage; expectations of learning rate and retention); (2) vocabulary assessment; (3) vocabulary teaching practices; (4) extensive reading; (5) technology; and (6) dictionary choice, use, and training. Participants expressed greatest interest in the following professional development topics: teaching techniques, learning strategies, assessment, the linking of classroom practice to research findings, and effects of repetition. Professional development in evidence-based best practices in these areas would enhance the teaching and learning of second language (L2) vocabulary.