Online teaching tools are effective means to engage students in online learning and thus, have been becoming increasingly popular in different educational settings. However, there is yet an increasing attention to implement these online teaching tools within a pedagogical method for a more engaging and effective learning. This paper is set out to explore the impact of FlipGrid application (henceforth, FlipGrid app) within metacognitive approach on students' speaking achievement and communication engagement. An exploratory case study using mixed-method research involving a one-group pre-and post-test design was employed in the study. A group of 29 Thai EFL first year college students was purposively selected as samples. A FlipGrid scaffold support table was also used to aid students on their speaking performance. Furthermore, a questionnaire on students' communication engagement was administered to assess the students' levels of communication engagement towards their peers and their teacher using the application. Quantitative findings reveal that students' speaking presentation performance in terms of the four speaking components such as clarity, content, delivery, and fluency and coherence, was improved. Moreover, majority of the participants agreed to the helpful affordances of FlipGrid app as their communicative engagement with their peers was enhanced. Qualitative results also revealed that the participants have positively welcomed the use of FlipGrid app in improving their speaking skill and communication engagement. Finally, the study findings offer considerable insights into utilizing FlipGrid app within a metacognitive approach to improve students' speaking performance, enhance their communication engagement, and transform language learning classroom in a modern technology-based environment especially in this time of pandemic.