In this research the relationship between sustainability and financial performance and the effect of (farm) size on this relationship will be investigated. First several theories explaining this relationship will be presented. Secondly, using data of the Farm Accountancy Data Network, sustainability indicators will be regressed against financial performance indicators. Following from the regressions, a positive relationship between sustainability and financial performance is found depending on the financial and sustainability indicator used and a negative effect of size (increase) on this relationship. Finally, recommendations and limitations of the research will be given.