The purpose of this qualitative interpretive study was to understand the ways teachers were influenced in their curricular and instructional decision-making processes in a freshman level mathematics class. Understanding what influences teachers' decision-making processes, and how (the ways) these processes were influenced, may lead to improved practice and ultimately improved student learning. Data collection was from three purposefully selected participants at a Midwestern, midsize university and consisted of a two-part journal, questionnaire, and follow up interviews. The follow up interviews were after each data collection for a total of three interviews. The data were analyzed using Hatch's (2002) models of typological analysis, inductive analysis, and interpretive analysis. Codes, categories, and themes of the data were developed by using a thematic analysis by Braun and Clarke (2006). The key findings included what factors and how these factors influenced a teacher's curricular and instructional decision-making processes in a freshman level mathematics class. Many factors were found such as internal, external, constraints, positive, negative, coordinator position, piloting courses, and committee work. Implications of these findings may impact how teachers make decisions, decrease cognitive loads while teaching, influence teacher training and education, and may improve teacher practice and student learning. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]