The National Research Council developed the concept of mathematical proficiency as being described by five strands: conceptual understanding, procedural fluency, strategic competency, adaptive reasoning, and productive disposition. The purpose of this study is to explore in-service mathematics teachers' perceptions of professional development needs related to the five strands of mathematical proficiency and to investigate the effect of teachers' demographic factors on their perceived needs. Participants included 342 teachers with varying qualifications and years of experience teaching at multiple grade levels (elementary, preparatory, and secondary) in Qatar's government schools. The study uses a 35-item questionnaire to evaluate teachers' professional development needs within the five strands.