The Mongols established an empire that ruled over two thirds of Eurasia. This was achieved, so they believed, by the will of heaven. Therefore, they had a great interest in reading the sky for guiding their earthly activities. Under the patronage of Mongol rulers, astronomers in both Yuan China and the Ilkhanate of Iran developed an extensive scholarly network and the astral sciences in both khanates witnessed their heyday. This paper reconstructs and compares the dynamic networks of astronomers in Ilkhanid Iran and Yuan China. Based on the astronomers’ biographies, it analyzes the wider culture of expertise and social settings that shaped the profession of heavenly observation and predictive analysis. The comparative perspective will highlight the continuities and changes of astronomy in China and Iran under Mongol rule. I will also discuss the achievements and limitations of the cross-cultural reading of heaven in Mongol Eurasia.