Novice nurses' mental health assessment practice is characterised by lack of consistency, despite mental health assessment being a core issue in professional nursing and patient safety across health services. This study aimed to identify mental health signs relevant for an assessment tool suitable for student and novice nurses. A document analysis approach was applied, and content analysis was used to analyse data extracted from carefully selected documents. Four main categories of mental health issues were identified: risk issues, symptom issues, psychological issues and self-care issues. Mental health signs were thereafter grouped in ten sub-categories characterising mental health concerns. These were: risk concerns, psychotic concerns, mood, affect and energy concerns, substance use concerns, somatic concerns, perception concerns, communication concerns, cognitive concerns, anxiety concerns and self-care concerns. The identified signs are considered relevant for student and novice nurses to learn and can be further developed into a clinical assessment tool for use in nursing education to strengthen mental health assessment competence in nursing education.