Type 2 diabetes mellitus (T2DM) is a common non-communicable disease that is associated with a high morbidity and mortality burden in patients, largely due to cardiovascular disease (CVD). There is a high prevalence of erectile dysfunction (ED) in men with T2DM across global populations. This reflects the links between ED and CVD, as well as shared risk factors for CVD and T2DM, where ED may serve as an early marker for disease. This chapter examines the biochemical and physiological connections between glycaemic control and erectile function and the importance of chronic hyperglycaemia in driving neurological and vascular mechanisms associated with the development of ED. There is a complex interplay between cardiovascular risk factors, comorbidities, hyperglycaemia and endothelial dysfunction in patients with ED, which is important when guiding patient care. The relevance of ED as an early marker for T2DM is considered in light of this complex dynamic, providing a basis for using ED as an opportunity to screen for hyperglycaemia and associated risk factors/comorbidities. Furthermore, the importance of considering ED in patients with T2DM is emphasised, summarizing recent guidelines and providing expert insights into how ED evaluation may be integrated into T2DM care processes.