Penulis mengadakan penelitian kualitatif ini bertujuan untuk menganalisa proses interaksi kelas pada proses belajar dan mengajar dalam pembelajaran kosa kata bahasa Inggris melalui permainanan guessing dan untuk menganalisa pola interaksi kelas berdasarkan pada model Initiation-Response-Feedback (IRF) yang penggunaannya disarankan oleh Sinclair and Coulthard. Penulis meneliti partisipasi siswa selama proses belajar mengajar menggunakan video perekam, kemudian penulis menjelaskan interaksi dan mengkatagorikan data dengan memberikan kode rekaman yang diusulkan oleh pola Sinclair and Coulthard. Hasil dari analisa data menunjukkan bahwa terdapat enam pola pertukaran yang terjadi sepanjang penerapan permainan guessing. Enam pola tersebut adalah Teacher Elicit (Initiation-Response-Feedback) 32,9%, Student Elicit (Initiation-Response/IR) 22,4%, Student Inform (Initiation-Feedback/IF) 16,8%, Teacher Inform (Initiation/I) 12,4 %, Teacher Direct (Initiation-Response-Feedback/IRF) 10,6 %, dan Check (Initiation-Response-Feedback/IRF) 5,0 %.The writer conducted this qualitative research to analyze the process of classroom interaction in teaching and learning process in English teaching vocabulary through guessing game and to analyze the pattern of classroom interaction based on Initiation-Response-Feedback (IRF) model suggested by Sinclair and Coulthard. The writer observed the participation of students during the process of teaching and learning using video recorded, then the writer transcribed the interaction and then categorized the data by giving a code the transcription suggested by Sinclair and Coulthard patterns. The result of data analysis shows that there are six exchange patterns happened during the implementation of guessing game. It is Teacher Elicit (Initiation-Response-Feedback/IRF) 32, 9%, Student Elicit (Initiation-Response/IR) 22,4%, Student Inform (Initiation-Feedback/IF) 16,8%, Teacher Inform (Initiation/I) 12,4 %, Teacher Direct (Initiation-Response-Feedback/IRF) 10,6 %, and Check (Initiation-Response-Feedback/IRF) 5,0 %.Keywords : classroom interaction, guessing game, vocabulary