One alternatively certified elementary teacher was the subject of this sixteen week research study on science teaching self-efficacy. The researcher taught inquiry based student level science lessons to the fourth grade teacher. The teacher participant, in turn, taught those same lessons to her class while the researcher observed and took field notes. The participant responded to specific open ended questions in a journal after each science experience and also completed three interviews with the researcher. Each sequential lesson from the researcher was then modified based on participant needs. The participant completed the STEBI (Science Teaching Efficacy Belief Instrument) as a pre and post test to measure the effects of the above mentioned activities. The collected data from the STEBI was reported quantitatively. The collected data from the reflective journal entries and interviews were reported qualitatively. After careful analysis of the data gathered for this case study, the researcher came to the conclusion that inquiry based professional development through the use of a mentor affected the alternatively certified elementary teacher's science teaching self-efficacy. The subject maintained a positive attitude about the use of a mentor for the duration of the study and her Personal Science Teaching Efficacy increased or stayed the same on all of the STEBI questions. Limitations of the study as well as recommendations for further research were also discussed.