Harmonisation of laws with the aim of increasing legal certainty and predictability has been on the agenda for decades. Particularly in the field of international trade, replacing multiple scattered national legislation and international regulations with uniform laws is of paramount importance since it can facilitate trade by mitigating the costs associated with acquiring information about different laws and adapting to them. The Convention on the International Sale of Goods (CISG) is one of these efforts. The overall success of international instruments purporting to create legal harmonisation is to be assessed based on the level of acceptability and certainty that they have. Still, 40 years after the adoption of this instrument, half of the Governments and some of the major economies including the UK, India, and South Africa have not ratified it. Criticisms have been received from Governments and lawyers about the certainty of its provisions. But how have the Governments approached the CISG and what are the necessary reforms in the light of trade and sustainable development? Drawing on a qualitative research this article attempts to answer this question and prove the hypothesis that the CISG needs to be reformed in order to meet modern global requirements. Therefore, it analyses the status of the CISG in the context of trade and the approach of States. Next, the development of international trade and sustainable development requirements have been analysed as an aspect of the global changes that reveal the weaknesses of the convention and call for the reform of this instrument.