This paper investigates green investments in energy and mining firms in South Africa to determine the efficiency level in terms of overinvestment and underinvestment. The general Richardson residual measurement model is employed, and an enhanced model is created by including variables that influence green investment, such as political connections and pollutant emissions. Data from 17 companies (5 energy and 12 mining) were used because of the significant effects of their operations on the environment over the period between 2015 and 2022. The study findings show that, in comparison to the estimated optimal investment level, South African energy and mining firms are not consistent regarding their investment level. It interplays between underinvestment and overinvestment. However, both firms demonstrated the tendency to green investment inefficiency due to underinvestment recorded in the latter years of the sample period. The study provides understanding as regards green investment levels of energy and mining firms and hence recommends adequate oversight and formulation of environmental policy by the government to ensure green investment efficiency in line with both national and international policies and regulations to facilitate a sustainable environment.