Suicide has been recognized as a major public health problem with high burden in low and middle income countries. Suicide has long lasting psychological trauma on friends and relatives in addition to loss of economic productivity. Although the need of high quality evidence is essential for designing suicide prevention program, Nepal lacks reliable evidence from nationally representative data. This study aimed to estimate the prevalence of suicidal ideation and attempt among adolescent students and identify the factors associated with them.Total of 6,531 students of grade 7 to 11 from 74 schools representing all three ecological belts and five development regions participated in this cross sectional study. To select the representative sample from study population, two stage cluster sampling method was used. Standardized self-administered questionnaire were completed by participants. Multivariable logistic regression was done to identify the factors associated with suicidal ideation and attempt.Nearly 13.59% of the participants had considered suicide while 10.33% had attempted it. Food insecurity (OR = 2.32, CI = 1.62-3.32), anxiety (OR = 2.54, CI = 1.49-4.30), loneliness (OR = 2.51, CI = 1.44-4.36) and gender (OR = 1.39, CI = 1.03-1.89) were identified as risk factors of suicidal ideation. Anxiety (OR = 3.02, CI = 1.18-7.74), loneliness (OR = 2.19, CI = 1.28-3.73) truancy (OR = 1.99, CI = 1.40-2.82), cigarette use (OR = 3.13, CI = 1.36-7.23) and gender (OR = 1.60, CI = 1.07-2.39) were identified as risk factors of suicidal attempt. Having 3 or more close friends was found to have protective effect (OR = 0.35, CI = 0.16-0.75) against suicidal attempt.Study reveals relatively high prevalence of suicidal ideation and suicidal attempt among school-going adolescents in Nepal. Appropriate coping strategies for factors like anxiety, loneliness seem could be useful for preventing both suicidal ideation and attempt.