Many global agricultural problems, such as the decline of agricultural land, soil pollution, climate change, water scarcity, and rural poverty threaten the sustainability of agricultural production systems. This study aimed to (i) develop a methodology to measure the sustainability of beef cattle farms, (ii) measure economic, social and environmental sustainability, and (iii) determine the impact of farm size on the sustainability of beef cattle farming. The study data were collected from 155 beef cattle sample farms via face-to-face surveys in Samsun Province, Turkey. A multi-stage process was employed to measure sustainability. The most important factors contributing to sustainability were determined as the debt-asset ratio, beef yield, and production cost for economic sustainability; the adequacy of educational institutions in the village or district and misunderstanding with neighbours for social sustainability; paying attention to meteorological conditions for pesticide use and nature conservation for environmental sustainability. The composite sustainability index was determined as 0.43 in small farms, 0.51 in medium farms and 0.61 in large farms. It has been found that an increase in the farm size had a positive impact on economic, social, and environmental sustainability of beef cattle farming. The methodology and indicators developed can be used to ensure the sustainability of different agricultural sectors.