Mathematics is one of the core school subjects that needs to be mastered across the world. Yet, some students consistently lag behind their peers in their mathematical performance no matter how hard they try. These students may have the possibility of having mathematical learning difficulties, which are characterized by, among other things, persistent failure in acquiring number concepts and developing arithmetic skills. Mathematical learning difficulties are found in students across different cultures. However, most studies on mathematical learning difficulties are conducted in Western countries; studies in Asian countries are relatively limited. In the past decade, mathematical learning difficulties have received more attention in Hong Kong. In this chapter, the authors review the recent research findings on mathematical learning difficulties among students in Hong Kong, as well as the assessment of and intervention for these students. Finally, the authors discuss the challenges and future direction of advancing our understanding of mathematical learning difficulties.