This study aimed to identify the practice extent of mathematics and science teachers of professional development activities, its sources and obstacles at elementary schools in Najran, and its relationship with specialty, gender, number of training courses. To achieve the study aims, the research questionnaire was prepared and consisted of (70) items distributed to three fields related to the activities, sources, and obstacles of the professional development in curriculum developed of the American McGraw Hill Education. Validity of the questionnaire was asserted by submitting it to a number of specialist arbitrators. Reliability was also verified and Cronbach Alpha correlation coefficient was (0.97). The study sample consisted of (201) teachers among which (103) mathematics teachers and (98) science teachers who were all teaching the developed mathematics and science curricula at the elementary schools in Najran during the academic year 2014/2015. Findings showed that the practice level of teachers' practice degree of professional development activities was moderate. The sources of which they receive professional development programs and obstacles they face were moderate, too. Results indicated that there were no statistically significant differences due to specialization and training courses, while there were significant differences (a = 0.01) among teachers with regard to the practice degree of professional development activities and the number of training courses due to gender in favor of females. The study recommended paying attention to the programs of teachers' professional development and their participation to meet their needs and requirements to attend conferences, seminars, workshops at the universities.