The research aims to determine the effect of character building in full day school on the students' character strengthening through school enviroment. This research used descriptive verification method with survey approach. The population in this research is all students at the eighth grade in SMPN 9 Bandar Lampung which with the total of 281 students and a sample of 165 respondents. Data collection was done by using quistionnaire of analysis technique by linear regression and path analysis. The result showed that there is a significant effect of character building in full day school and school enviroment to students' character. That analysis showed students' character is influenced by any variables of character building in full day school and school enviroment of 21.7% and the remaining 78.3% is influenced by other factors which are not examined in this research.Penelitian ini bertujuan untuk mengetahui pengaruh character building dalam full day school terhadap penguatan pendidikan karakter melalui lingkungan sekolah. Penelitian ini menggunakan metode deskriptif verifikatif dengan pendekatan survey. Populasi pada penelitian ini yaitu seluruh siswa kelas VIII SMP Negeri 9 Bandar Lampung dengan jumlah sebanyak 281 siswa dan sampel sebanyak 165 siswa. Pengumpulan data dilakukan menggunakan kuisioner. Teknik analisis menggunakan Regresi Liniear dan Path Analysis. Hasil penelitian ini menunjukkan bahwa ada pengaruh character building dalam program full day school dan lingkungan sekolah terhadap penguatan pendidikan karakter. Berdasarkan analisis data diketahui bahwa penguatan pendidikan karakter dipengaruhi oleh variabel character building dalam program full day school dan lingkungan sekolah sebesar 21,7% dan sisanya 78,3% dipengaruhi oleh faktor lain yang tidak diteliti dalam penelitian ini.Kata kunci : character building, full day school, lingkungan sekolah dan penguatan pendidikan karakter