This two-phase sequential mixed methods study examined the relationship between professional development, whether in the form of traditional professional development, a professional learning community and/or lesson study, and teacher self-efficacy and self-directed learning in order to gain a greater understanding of the role professional development plays in teacher identity and efficacy as they relate to adult learning theory. The qualitative case study method was used to interview 22 teachers, half of whom participated in a professional learning community known as lesson study. The interview data indicated that collaboration was simply one of the variables that influenced teacher efficacy and identity. Each teacher expressed high levels of conscious self-directed learning tendencies, a hallmark of adult learning theory, indicating a relationship between self-directed learning and identity, efficacy, and collaboration; however, analysis of the data did not provide enough information to determine which variables were the cause and which were the effect. A modified version of the Personal Learning Orientation to Self Direction in Learning Scale (PRO-SDLS) (Stockdale & Brockett, 2011) was sent to approximately 600 teachers in two school districts. The research hypotheses stated that high self-efficacy scores and self-directed learning scores were the result of participation in a professional learning community and that participation in lesson study would result in higher self-efficacy and higher self-directed learning scores than participation in a professional learning community. The hypotheses were answered by running "t" -tests and a one-way MANOVA. Results suggest that participation in a professional learning community did not affect teacher self-efficacy; however, participation in a professional learning community affected self-directed learning as measured by motivation but not initiative or control. Results from a one-way MANOVA indicate that participation in lesson study affects self-directed learning as measured by initiative, control and motivation, but not self-efficacy. Collaboration is an important factor in promoting teacher-efficacy, but that collaboration may take many forms, including a professional learning community. Future research studies examining collective teacher efficacy and other types of teacher collaboration may be useful in determining the role these variables play in how teachers learn and develop self-efficacy and identity. [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.]