This study evaluates telecommunications industry efficiency in 19 countries grouped into high income countries (HICs) and middle income countries (MICs). Using data from 2001-2013 and a two-stage Data Envelopment Analysis (DEA), it finds that while HICs outperformed MICs, both of the groups exhibited improved technical efficiency, managerial effectiveness, and operational scale. Additionally, time in deregulation enhances technical and scale efficiency in HICs, however, the influence is insignificant in MICs. Labour productivity drives technical efficiency in HICs. Also, it augments managerial resourcefulness in HICs and MICs, however, its influence on scale efficiency is immaterial. Revenue per subscription enhance technical efficiency and managerial effectiveness in the two groups of countries. The relationship with scale efficiency, which is positive in HICs is irrelevant in MICs. Capital intensity has insignificant influence on managerial effectiveness in the two clusters of countries, however, it undermines technical efficiency in HICs and scale efficiency in MICs. Gross national income per capita is inconsequential to scale enhancement. However, it contributes to technical efficiency in the two categories of countries and managerial performance in HICs. Efficiency performances in HICs and MICs are insensitive to the industry's concentration level. Inflation has insignificant influence on scale efficiency in HICs and MICs. Also, it drives technical efficiency and managerial performance in MICs, but the influence in HICs is immaterial. The joint impact of labour productivity and capital intensity is irrelevant to operational scale in HICs and MICs, however, it is negatively associated with technical efficiency and managerial effectiveness in MICs. This empirical study provides additional insight that managers in the industry and policy makers will find useful during strategy formulation and policy deliberations.