The objectives of this research were to (1) Develop the lesson plans by using a Flipped Classroom through a 3D Virtual classroom with Metaverse Spatial, (2) Compare the grammar achievement after implementing a Flipped Classroom through a 3D Virtual classroom with Metaverse Spatial, and (3) Explore the students' satisfaction for using a 3D virtual classroom with Metaverse Spatial. This research was a quantitative experimental research design. The sample group comprised 33 students in Grade 9, semester 2, and the 2022 academic year, obtained from Custer random sampling. Research materials and instruments included (1) Lesson plans, (2) A Grammar achievement test, and (3) Students' satisfaction questionnaire. The data were analyzed using percentages, descriptive statistics (Mean and Standard Deviation), and t-tests. The results showed that (1) The lesson plans using a Flipped Classroom through a 3D Virtual classroom with Metaverse Spatial were developed at the "most suitable" level M=4.57, SD=0.17), (2) To compare the grammar achievement after using Flipped Classroom through 3D virtual classroom with Metaverse Spatial was higher at statistically significant levels 0.05, and (3) The students' satisfaction was averaged at M=4.68, SD=0.67 mean the students concern with the highest satisfaction using a Flipped Classroom through 3D Virtual classroom with Metaverse Spatial. The study demonstrated that through a 3D Virtual classroom with Metaverse Spatial, the Flipped Classroom notably enhances grammar achievement and aligns with contemporary educational practices and technological advancements. The Flipped Classroom through the 3D virtual classroom with Metaverse Spatial amended grammar achievement.