Aim The aim of this study is to determine the factors affecting insomnia in nursing students. Methods This study was conducted with 379 nursing students, studying at a university in western Anatolia/Turkey between 2014 and 2015 as a descriptive and cross‐sectional analytic study. Data of the survey were collected using the Personal Inquiry Form, Pittsburgh Sleep Quality Index, Insomnia Severity Index, Trait Anxiety Inventory and the Beck Depression Inventory, and a self‐administered questionnaire. Results The Insomnia Severity Index score for the students is 11.51 ± 5.04 on average. It was found that as anxiety and depression increased, the Insomnia Severity Index score for the students also increased and there was a weak positive correlation. Also, a moderate positive correlation between sleep quality and insomnia severity was found. Significant correlations were found between some of the socio‐demographic characteristics (lower socio‐economic situation, irregular bedtime, and smoking) and insomnia, sleep quality, anxiety, and depression. Conclusion Anxiety, depression, irregular bedtime, and lower socio‐economic situation are factors that make falling asleep difficult. SUMMARY STATEMENT What is already known about this topic? Insomnia is a common problem in the college students of many countries. There are many causes of insomnia as inadequate sleep hygiene, caffeine and energy drink consumption, stimulants and alcohol use, technology, uncomfortable sleeping environments, workload, anxiety, depression, and female gender. Little research has investigated what factors are associated with sleep disorders in nursing students. What this paper adds: Economic condition, smoking, depression, trait anxiety, and going to bed irregularly are important factors affecting sleep among nursing students. Insomnia severity was considerably higher in the students whose bedtime was irregular than in the students whose bedtime was regular. The implications of this paper: It is suggested that awareness of the relationship between alcohol/caffeinated beverage consumption and sleep quality should be increased to increase sleep quality of university students. Moreover, seminars and conferences about sleep hygiene should be organized for the university students.