Social contagion, the process whereby psychological states spread from one person to another, is a pervasive phenomenon. However, this has not been adequately explored in the educational context, especially in relation to the social contagion between principals and teachers. This study aimed to examine the social contagion of job satisfaction from principals to teachers and its implications for instructional quality (i.e., clarity of instruction and cognitive activation). We made use of the Teaching and Learning International Survey (TALIS) 2018 data and drew on 47,315 teachers and 3008 principals from two cultural groups: Confucian societies (Japan, Taiwan, Korea, and Shanghai) and English-speaking societies (Canada, Australia, New Zealand, United States, and United Kingdom). Results of multilevel mediation analyses revealed that principal job satisfaction was related to teacher job satisfaction, providing support for the principal-teacher job satisfaction contagion. The job satisfaction contagion was subsequently associated with teachers' clarity of instruction and cognitive activation in Confucian societies, but only cognitive activation in English-speaking societies. Teacher job satisfaction was associated with both instructional quality indicators in both cultural groups. The study provided evidence of the social contagion of job satisfaction between principals and teachers. Study results also demonstrated how the contagion of job satisfaction is subsequently associated with teachers' instructional quality across different cultural contexts.