This paper theoretically examines and empirically assesses the ethical statements by Pope Francis and Patriarch Bartholomew in terms of their ability to achieve global environmental sustainability. The theological discussion of environmental precepts in documents/speeches based on the recent academic literature suggests that (absolute feasibility) Pope Francis pursues unfeasible environmental and social goals (personal fulfillment, poverty reduction, population growth), whereas Patriarch Bartholomew pursues feasible environmental goals (meeting God’s will, following God’s law); (relative feasibility) Pope Francis suggests unclear and inconsistent values, whereas Patriarch Bartholomew suggests clear and consistent values; (absolute reliability) Pope Francis relies on many instruments close to alternative attitudes to the environment (happy sobriety, contemplative style, human rights), whereas Patriarch Bartholomew rests on few instruments close to unambiguous concerns for the environment (happiness from sanctity, ascetism, duties to community); (relative reliability) Pope Francis suggests broad behavioral rules, whereas Patriarch Bartholomew suggests targeted behavioral rules. The statistical analysis of documents/speeches as if they are environmental regulations (using “sin”) based on dynamic panel data shows that Patriarch Bartholomew > Pope Francis in absolute feasibility; Patriarch Bartholomew > Pope Francis in relative feasibility; Pope Francis > Patriarch Bartholomew in absolute reliability; and Patriarch Bartholomew > Pope Francis in relative reliability. Pope Francis and Patriarch Bartholomew together reduced the global average per capita use of the Earth’s resources by 5% per year.