Achieving sustainable food and nutrition security is dependent on enhancing dietary diversity to address micronutrient deficiency. Biodiversity, which includes diversity within and between species and of ecosystems, is crucial for dietary diversity, a qualitative measure of food variety available for individual and household consumption and a proxy for nutritional adequacy. This paper explores the poorly understood relationships between biodiversity (including agro-biodiversity) and dietary diversity in the Mediterranean area. It is based on an extensive yet targeted literature review carried out using Google search engine to capture important scholarly and grey literature mainly in the periods February-June 2015 and January-April 2016. FAO food supply data from 21 Mediterranean countries show that in the period between 1990-92 and 2007-2009, dietary diversity increased in most countries through a reduction in the contribution of starchy, staple foods to total energy and an increase in consumption of protein from animal origin. Meanwhile, reviewed literature shows that there was over the last decades a general decline of biodiversity and agricultural biodiversity in the Mediterranean region. These contradictory trends affecting Mediterranean dietary patterns may reflect rising affluence and trade liberalisation. The paper also highlights that the dietary polymorphism that has existed in the Mediterranean for millennia, which reflects biological and cultural diversity, is under threat with the erosion of food culture and biodiversity-related knowledge. Further studies, using dietary surveys rather than apparent consumption food supply data and valid dietary diversity scoring methods, are needed to enable a more accurate and evidence-based monitoring of dietary diversity in different Mediterranean countries. Nevertheless, safeguarding and promoting the Mediterranean diet and its inherent diversity is vital for conserving the extraordinary cultural, biological and dietary diversity in the region. Insights provided by the present paper should be taken into consideration in formulating effective policies to deal simultaneously with malnutrition (especially micronutrient deficiencies) and biodiversity loss in the Mediterranean area.