This sequential mixed methods case study was conducted in a mathematics class in a Midwestern university to determine whether exposure to constructivist mathematics teaching would influence change in the mathematics teaching efficacy beliefs of preservice elementary teachers. The study examined the instructor’s beliefs and pedagogical practices and how they affected her students in two sections of geometry for a sixteen-week semester. Qualitative data collected and analyzed included a course syllabus, instructor-selected textbook, observation notes, instructor and student reflections, photos of student work, and interviews. Quantitative data was collected using a version of the Mathematics Teaching Efficacy Beliefs Instrument (MTEBI) (Enochs, Smith, & Huinker, 2000) adapted and validated for preservice elementary teachers. Qualitative data from the instructor indicated recurring themes of the instructor’s use of humor, wait-time, questioning, persistence, encouragement, negotiation, and repetition. These themes fall generally into two broad pedagogical categories: care and technique. The quantitative data on the students from the MTEBI indicated insignificant (p > .05) positive change in both the personal mathematics teaching efficacy and the mathematics teaching outcome expectancy. However, the qualitative data on the students indicated significant positive effect on their mathematics teaching beliefs as indicated throughout the semester by the words they used in their reflections, their engagement in classroom community, and their conversation and questions during class. Recurring themes observed throughout the study indicated a progression in student response from struggle and frustration to confidence and community, a progression which can be interpreted as an indication of positive change in the preservice teachers.