The recognition of forage production methods that maximize energy efficiency and minimize Greenhouse Gases (GHGs) emissions is essential. The aims of this survey were to assess the energy consumption, emissions of GHGs and global warming potential (GWP) of alfalfa production systems in Sistan region, Sistan and Baluchestan province in the South–east of Iran. Data were collected randomly from 110 alfalfa farm using face-to-face questionnaire survey. Energy inputs included chemical fertilizers, diesel fuel, pesticides, seed, machinery and human labor. The results indicated that average total input and output energies in alfalfa production during the entire lifetime of the farm were 313.52GJha−1 and 962.85GJha−1, respectively. The most important energy inputs belonged to electricity (72.5%), followed by diesel fuel (12.3%) and N fertilizer (6.0%). Energy use efficiency and energy productivity were 3.07 and 0.209kgMJ−1, respectively. Share of direct and indirect energy were 85% and 15%, respectively. Total emissions of CO2, N2O and CH4 in alfalfa farms were 8262.67kgha−1, 557.31kgha−1 and 7.65kgha−1, respectively. Hence, total GWP was 181190 kg CO2eha−1 and 2.77 kg of CO2ekg−1 of dry hay produced. In terms of CO2e, 95.3% of the GWP originate from N2O, 4.6% from CO2 and 0.1% from CH4. Accordingly, efficient use of energy is essential to reduce the greenhouse gas emissions and environmental impact in alfalfa agroecosystems