Background: Mental illness is considered a clinically significant behavioral or psychological syndrome marked by distress, disability, or the risk of suffering, disability, or loss of freedom (APA, 2007). Mental illness causes a mild to severe disturbances in thought and/or behavior, resulting in an inability to cope with life’s ordinary demands and routines. The common sign and symptoms of mental illness are decreased sleep, sometimes increase anger, decrease self care, increase talk or sometimes decrease interaction, loss of appetite, thought disturbances, perceptual disturbances, abnormal behavior, fearfulness, suicidal thoughts etc. The most frequently detected needs of the patients by staff in the area concerning psychotic symptoms, daytime activity, physical health and information about their condition and treatment. Aim of the study: To assess the nursing needs among patients with mental illness. Objectives

1. To assess the socio-demographic profile of patients with mental illness admitted at Tertiary care Hospital, Assam.
2. To find out the clinical variables of the patients with mental illness.
3. To assess the nursing needs among patients with mental illness admitted at Tertiary care Hospital at different point of time i.e. on 1^st, 3^rd, 14^th and 30^th days of hospitalization from patient’s files.

Material and methods: Research Approach: A qualitative approach and historical retrospective design with a total of 30 samples of patient’s files (10 schizophrenia, 10 mood disorder and 10 substance use disorder) were included in the study. Purposive sampling technique was used for selecting the sample. Socio-demographic data sheet and observation of nurse’s notes and other professional notes documentation in patient’s files was used. The notes on the 1^st day, 3^rd day, 14^th day and 30^th day of hospitalization were considered for data collection. Analyses were done manually and analyzed by systematic text condensation inspired by Goirigi (content and thematic analysis). Results: In this study, it has been revealed that 1^st day, 3^rd day, 14^th day and 30^th day of hospitalization the nursing needs are different in all domain and also nursing needs are significantly differs in patients with schizophrenia, substance use disorder and mood disorder. From the evidence based findings of the study it was also found that the nursing needs are different according to their severity of symptoms and illness of the patient’s.