Assessment is an important aspect of mathematics teaching and learning. This paper aims to explore Hong Kong mathematics teachers’ views on online assessment during the COVID-19 pandemic. The data analysed is part of a larger project comprising an online survey and semi-structured interviews. This paper presents data from the survey responses of ninety-two teachers and from interviews of three teachers. Thematic data analysis is conducted, focusing on teachers’ views on assessment during online learning. Findings show that the forms of assessment that Hong Kong mathematics teachers conducted during the pandemic were similar to those from before the pandemic. They view online assessment mainly as assessment for and of online learning. This paper also discusses suggestions for online mathematics assessment. Copyright © 2022 left to the authors.