At one local school site in Georgia, a subgroup of students did not achieve a score of at least 800 on the state's Criterion Referenced Competency Test in math. To improve student success, the local site implemented professional development (PD) for teachers. Successful PD has been shown to promote effective teaching practices, which in turn, have resulted in improved student learning. The purpose of this phenomenological study was to explore 5th grade teachers' lived experiences of PD and its influence on their application of the Common Core state standards. Bandura's social cognitive theory of self-efficacy guided the study. In-depth interview data were gathered from 5 teachers who taught 5th grade and experienced at least 3 PD sessions. Data from the interviews were transcribed, open coded, and then analyzed with the interpretive model in search of common themes. The 5 teachers' narratives identified ineffective and irrelevant PD and insufficient math resources for teaching the state's math standards. Based on the findings, 3 original PD sessions on the planning and implementation of the state standards were created and additional training and resources were recommended to the local site. This study may promote positive social change by helping local teachers improve their instruction of the state's mathematics standards, thereby improving the mathematics education of students.