Gastroenteritis Akut (GEA) adalah penyakit peradangan pada saluran pencernaan yang dapat menginfeksi dan mudah menyebar serta memiliki tingkat morbiditas dan mortalitas yang tinggi terutama di Negara berkembang seperti Indonesia. Tujuan penelitian ini untuk mengetahui tingkat pengetahuan dan perilaku pasien tentang penyakit GEA di ruang rawat inap. Jenis penelitian ini adalah kuantitatif deskriptif dengan populasi seluruh pasien dewasa yang mengalami GEA dan sampel didapatkan dengan teknik “Total Sampling” sebanyak 30 responden serta pengumpulan data menggunakan kuesioner, yang dilakukan pada bulan Juni 2018 hingga Juli 2018. Hasil penelitian menunjukkan bahwa dari 30 responden pasien dewasa yang mengalami GEA yang dirawat di Rumah Sakit Swasta di Indonesia Barat terdapat 12 responden (40%) yang memiliki pengetahuan baik, 12 responden (40%) berpengetahuan cukup dan 6 responden (20%) memiliki pengetahuan yang kurang. Berdasarkan perilaku didapatkan hasil 23 responden (77%) memiliki perilaku yang baik dan 7 responden (23%) memiliki perilaku cukup. Dari hasil keseluruhan tentang gambaran tingkat pengetahuandan perilaku pasien dewasa tentang penyakit Gastroenteritis Akut di ruang rawat inap Rumah Sakit Swasta Di Indonesia Barat, responden menunjukan pengetahuan dan perilaku yang baik terhadap penyakit yang dideritanya = Acute Gastroenteritis (AGE) is an inflammatory disease of the gastrointestinal tract that can infect and spread easily and has a high rate of morbidity and mortality especially in developing countries such as Indonesia. One way to manage the AGE disease is to increase the knowledge and behavior of the patient. The purpose of this study is to determine the level of knowledge and behavior of patient about AGE disease in the inpatient wards. The type of this research is quantitative descriptive with the population of all adult patients who experienced AGE and the sample obtained by technique "Total Sampling" as many as 30 respondents and data collection using questionnaire that has been examine on validity and reliability. This study was conducted on June 2018 until July 2018. The results showed that, from 30 respondents of adult patients who experienced AGE treated in private hospital in western Indonesia there were 12 respondents (40%) who had good knowledge, 12 respondents (40%) was moderate and 6 respondents (20%) had less knowledge. Based on the behavior, it was found that 23 respondents (77%) had good behavior and 7 respondents (23%) was moderate. From the overview of the overall results of the description of the level of knowledge and behavior of adult patients on Acute Gastroenteritis disease in the private hospital wards in West Indonesia, the respondents showed good knowledge and behavior toward the illness.