Professional development (PD) for mathematics teachers in China, especially in Shanghai, has received growing international attention. However, most of available research concerning Chinese PD has focused on successful practices, and far too little attention has been paid to less successfully organized PD practices, particularly for mathematics teachers in Shanghai. This study aims to examine key aspects and underlying reasons for less successfully organized PD practices in Shanghai from teachers' perspectives. The data were collected from 132 mathematics teachers in 9 randomly selected secondary schools in Shanghai through a questionnaire survey and follow-up interviews. The results show that Shanghai mathematics teachers perceived "time, duration and frequency", "assessment and management" and "objective" as the three most unsatisfactory aspects in less successfully organized PD they attended, and they considered that organized PD practices were less successful mainly due to lack of assessment for the PD organizers and of necessary coordination between PD organizers at different levels. In addition, there were statistically significant differences in teachers' perceptions of various specific problems in different aspects about less successfully organized PD between teachers with different demographic features, such as length of teaching experience and gender. Implications of the findings of the study to Chinese educational settings and beyond are discussed at the end of the paper.