Teacher quality has received increasing focus over the past decade, yet, by some measures, teachers rarely improve after their first few years of teaching, and not all teachers seem driven to improve. Traditional models of professional learning have emphasized the processes that teachers take part in as a facilitator of their improvement. Research by Dweck suggests that implicit beliefs about ability can have a powerful influence on learning. The purpose of this study was to investigate how teachers' professional learning is influenced by their underlying goals and beliefs. In particular, this study tested a multiple linear path model that attempts to explain variation in teachers' professional learning activities. A new variable, teacher mindset, was developed to operationalize teachers' conceptions about the nature of teaching ability. The path model explores how teacher mindset, self-theories, teacher efficacy, and goal orientation interact to predict teachers' participation in professional learning activities. 312 teachers from 92 elementary schools in Los Angeles participated in a voluntary survey designed and pilot-tested by the researcher. Principal components factor analysis with varimax rotation generated five composite professional learning activity variables (PLAs). Through multiple regression analysis, teacher efficacy emerged as a significant predictor of four PLAs , while teacher mindset and learning goal orientation emerged as significant predictors of three PLAs. The path analyses provided strong support for the hypothesized model. The anticipated relationships between the variables appeared in most [3 out of 5 paths] of the analyses performed. Both in regression analyses and the path analyses, teacher mindset emerged as a significant predictor more frequently than any other variable. The findings suggest that the improvement of teachers may depend on the variables highlighted in this study, most notably teacher mindset. Implications for teacher education, professional development, and education policy are discussed. Further research should investigate the role of teacher mindset in other contexts and test the path model with other populations. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]