Background: The Canadian Network for Mood and Anxiety Treatments (CANMAT) publishes clinical practice guidelines for mood and anxiety disorders. This CANMAT guideline aims to provide comprehensive clinical guidance for the pregnancy and postpartum (perinatal) management of mood, anxiety and related disorders. Methods: CANMAT convened a core editorial group of interdisciplinary academic clinicians and persons with lived experience (PWLE), and 3 advisory panels of PWLE and perinatal health and perinatal mental health clinicians. We searched for systematic reviews of prevention and treatment interventions for perinatal depressive, bipolar, anxiety, obsessive–compulsive and post-traumatic stress disorders (January 2013–October 2023). We prioritized evidence from reviews of randomized controlled trials (RCTs), except for the perinatal safety of medications where reviews of large high-quality observational studies were prioritized due to the absence of RCT data. Targeted searches for individual studies were conducted when systematic reviews were limited or absent. Recommendations were organized by lines of treatment based on CANMAT-defined levels of evidence quality, supplemented by editorial group consensus to balance efficacy, safety, tolerability and feasibility considerations. Results: The guideline covers 10 clinical sections in a question-and-answer format that maps onto the patient care journey: case identification; organization and delivery of care; non-pharmacological (lifestyle, psychosocial, psychological), pharmacological, neuromodulation and complementary and alternative medicine interventions; high-risk clinical situations; and mental health of the father or co-parent. Equity, diversity and inclusion considerations are provided. Conclusions: This guideline's detailed evidence-based recommendations provide clinicians with key information to promote the delivery of effective and safe perinatal mental healthcare. It is hoped that the guideline will serve as a valuable tool for clinicians in Canada and around the world to help optimize clinical outcomes in the area of perinatal mental health. Plain Language Summary Title: The Canadian Network for Mood and Anxiety Treatments 2024 Guideline for Helping People with Mood, Anxiety and Related Disorders During Pregnancy and Postpartum