In the context of global climate change, vulnerability of farmland ecosystems in countries along the "Belt and Road" can directly affect regional food security. In this paper, we quantitatively analyzed the spatial distribution characteristics of farmland ecosystem vulnerability in countries along the "Belt and Road", as well as the responses to climate change. Results show: (1) Farmland ecosystems in countries along the “Belt and Road” generally had higher vulnerability, wherein 77.1% farmland ecosystems were found moderately and severely vulnerable. There was significant spatial variation of the farmland ecosystem vulnerability—higher in Central Asia, West Asia, and Mongolia; moderate in China, Southeast Asia, and South Asia; and lower in Russia, the Commonwealth of the Independent States, and Central and Eastern Europe. (2) Since 1980, farmland ecosystems along the "Belt and Road" have become notably warmer and drier, with the warming and drying area accounts for 64.06% and distributed mainly in central and southern China, the Commonwealth of the Independent States, southwestern Russia, Central Asia, Western Asia, western and southern India, Myanmar, Cambodia, and Indonesia. Warming and drying was the main feature of climate change in the farmland ecosystems of countries along the "Belt and Road". (3) Areas of climate change arranged per farmland ecosystem vulnerability from the lowest to the highest were: warm-wet areas, cold-wet areas, warm-dry areas, and cold-dry areas. The farmland ecosystem in the warm-wet areas was the least vulnerable and that in the cold-dry areas the most; the area of highly vulnerable farmland ecosystem in the warm-wet areas accounted for 43.09%, and that of highly vulnerable farmland ecosystem in the cold-dry areas accounted for 56.01%. Temperature and precipitation variations and their coupling relation controlled the vulnerability of farmland ecosystems, of which the trend of precipitation variation was an important factor influencing farmland ecological coordination and vulnerability. Our findings could serve as a useful reference to address the issue of food security in countries along the "Belt and Road", and to promote the sustainable agricultural development and enhance international cooperation with countries along the “Belt and Road” in agriculture.