With the development of synchronous videoconferencing technology, research on the professional practices of synchronous online teaching has been growing at an exponential rate. However, little is known about synchronous online teachers' use of motivational strategies, despite the important role of teachers in fostering student motivation. To address this gap, this mixed-methods study examined how synchronous online teachers utilized motivational strategies and explored the influence of the synchronous online environment on the use of motivational strategies. As an analytical framework, we drew on the need-supportive teaching principles of the self-determination theory, which present three types of motivational strategies: involvement, structure, and autonomy-support. The quantitative analysis of survey results collected from language teachers (N = 72) revealed the perception that autonomy-support and structure were relatively well suited to the online environment while involvement was difficult to implement. The qualitative analysis of follow-up interviews (N = 10) elucidated how the online environment influenced the teachers' use of each strategy while producing a new framework and specific strategy lists that may be applicable to synchronous online teaching. This study presents important theoretical implications regarding the application of self-determination theory in online education, while also providing practical implications for synchronous online teacher preparation and professional development.