At the UN in New York the Open Working Group created by the UN General Assembly proposed a set of global Sustainable Development Goals (SDGs) which comprises 17 goals and 169 targets. Further to that, a preliminary set of 330 indicators was introduced in March 2015. Some SDGs build on preceding Millennium Development Goals while others incorporate new ideas. A critical review has revealed that indicators of varied quality (in terms of the fulfilment certain criteria) have been proposed to assess sustainable development. Despite the fact that there is plenty of theoretical work on quality standards for indicators, in practice users cannot often be sure how adequately the indicators measure the monitored phenomena. Therefore we stress the need to operationalise the Sustainable Development Goals’ targets and evaluate the indicators’ relevance, the characteristic of utmost importance among the indicators’ quality traits. The current format of the proposed SDGs and their targets has laid a policy framework; however, without thorough expert and scientific follow up on their operationalisation the indicators may be ambiguous. Therefore we argue for the foundation of a conceptual framework for selecting appropriate indicators for targets from existing sets or formulating new ones. Experts should focus on the “indicator-indicated fact” relation to ensure the indicators’ relevance in order for clear, unambiguous messages to be conveyed to users (decision- and policy-makers and also the lay public). Finally we offer some recommendations for indicators providers in order to contribute to the tremendous amount of conceptual work needed to lay a strong foundation for the development of the final indicators framework.