Abstract : The purpose of this research was to find out the disruptive behaviour in the English class. This research was conducted to the eleventh grade students of SMA Adisucipto. Case study was used in conducting this research. The subject of this research was the eleventh grade students. The techniques of data collecting used in this research were observation, interview and documented observation. It was found in the research that talking without permission (D1) and (D2), and attention seeking (D3) were the highest observable disruptive behaviours in the class. The formers were because of boring or having less motivation in learning English, the later was because of having less attention from the teacher. Documented observation showed the test score of D1 and D2 were also low; good, but achieved through cheating of D3. It is suggested that the disruptive activities that occured during the class should be managed well. Keywords : Disruptive, Behaviour, English Abstrak : Tujuan dari penelitian ini adalah untuk menemukan perilaku-perilaku nakal di mata pelajaran bahasa inggris. Penelitian ini dilaksanakan terhadap siswa kelas 11 SMA Adisucipto. Studi kasus digunakan dalam melaksanakan penelitian ini. Teknik-teknik dalam pengolahan data antara lain observasi, interview, dan observasi dokumen. Ditemukan bahwa berbicara saat pelajaran (D1) dan (D2), dan mencari-cari perhatian (D3) merupakan prilaku nakal siswa yang paling sering ditemukan di dalam kelas. Perilaku yang pertama disebabkan oleh kebosanan dan kurangnya motivasi dalam belajar bahasa inggris, perilaku terakhir disebabkan oleh kurang nya perhatian dari guru. Observasi dokumen menunjukkan hasil tes D1 dan D2 sangat kurang, sedangkan D3 mempunyai hasil yang bagus akan tetapi melakukan kecurangan. Sangat disarankan bahwa aktivitas perilaku nakal yang terjadi selama dikelas harus di tindak lanjuti dengan baik. Kata kunci : Nakal, Tingkah Laku, Inggris