Few studies have been conducted to investigate the ethical perspectives of in-service teachers on assessment issues cross-culturally. The purpose of the study was to investigate the ethical judgment by in-service teachers in the United States and China on twenty scenarios of student assessment practices. In the spring of 2020, 130 American teachers and 161 Chinese teachers completed a survey questionnaire on these assessment scenarios. The quantitative and qualitative results indicated that respondents had different ethical decisions in 9 out of 20 scenarios. Further analysis indicated that there was a high degree of similarities in ethical reasoning, and 10 scenarios with mixed reasoning indicated that certain sub-themes were different. This study reveals that cultural differences are likely reflected in their ethical judgment when presented with certain assessment scenarios. The awareness of such differences should be raised by considering assessment, teaching, and learning together.