The European Green Deal announced by the European Commission in December 2019 is a roadmap meant to foster the transition of the European Union towards the climate-neutral economy by reducing carbon emissions towards 55% by 2030 and achieving carbon neutrality by 2050. By putting the EGD in a boarder perspective of evolving, constitutional rationale of environmental protection in the EU legal order, this contribution examines horizontal, legal dimension and financial implications of the green transition. The challenge ahead of the Union is now how to transform the ambitious climate agenda into efficient legal and economic instruments ‘in a fair way, leaving no one behind’. This paper argues that EGD is a great opportunity, but in order to turn it into a success, it must be strongly anchored in the concepts pertaining to the constitutional framework of the EU legal order, in particular, the concepts of solidarity, sustainable development and high level of environmental protection.