Background: The aim of this review was to assess the quality of international treatment guidelines for post-traumatic stress disorder (PTSD), and identify differences between guideline recommendations, with a focus on the treatment of nightmares. Methods: Guidelines were identified through electronic searches of MEDLINE, CINAHL, PubMed, Embase and Science Direct, as well as web-based searches of international guideline repositories, websites of psychiatric organisations and targeted web-searches for guidelines from the three most populous English-speaking countries in each continent. Data in relation to recommendations were extracted and the AGREE II criteria were applied to assess for quality. Results: Fourteen guidelines, published between 2004–2020, were identified for inclusion in this review. Only five were less than 5 years old. Three guidelines scored highly across all AGREE II domains, while others varied between domains. Most guidelines consider both psychological and pharmacological therapies as first-line in PTSD. All but one guideline recommended cognitive behavioural therapy (CBT) as first-line psychological treatment, and selective serotonin reuptake inhibitors (SSRIs) as first-line pharmacological treatment. Most guidelines do not mention the targeted treatment of nightmares as a symptom of PTSD. Prazosin is discussed in several guidelines for the treatment of nightmares, but recommendations vary widely. Most PTSD guidelines were deemed to be of good quality; however, many could be considered out of date. Recommendations for core PTSD symptoms do not differ greatly between guidelines. However, despite the availability of targeted treatments for nightmares, most guidelines do not adequately address this. Conclusions: Guidelines need to be kept current to maintain clinical utility. Improvements are most needed in the AGREE II key domains of ‘applicability’, ‘rigour of development’ and ‘stakeholder involvement’. Due to the treatment-resistant nature of nightmares, guideline development groups should consider producing more detailed recommendations for their targeted treatment. More high-quality trials are also required to provide a solid foundation for making these clinical recommendations for the management of nightmares in PTSD.