Physics is one of the science, technology, engineering, and mathematics (STEM) disciplines in which the participation of women is unacceptably low. The representation gaps among certain groups of students have motivated education researchers and practitioners to understand and address the underlying reasons for low diversity in physics. Despite an expanding effort in the physics community to increase the participation of women, only 20% of all bachelors' degrees in physics across the U.S. are currently earned by women. In this thesis, I focus on understanding the gendered differences in students' motivational characteristics in introductory physics courses for STEM majors and how they vary across time by investigating the relation between gender, physics performance, and motivational characteristics. In particular, I examined how physics self-efficacy, interest, perceived recognition, and intelligence mindset (e.g., belief that intelligence is either innate or can grow with effort) can predict students' physics course performance overall and on standardized conceptual physics assessments after controlling for prior academic preparation, SAT scores, high school GPA, and demographic variables. Physics is one of the pillar courses in first-year undergraduate STEM programs. Since these introductory courses are significantly influential for students' retention in STEM, I also examined the physics identity of students. Specifically, I studied female and male students' perception of how their peers and teaching assistants/instructors recognize them as someone who is good at physics. Findings showed statistically significant gendered patterns in each study conducted, revealing sizable gender differences in students' identity formation as examined through the selected motivational constructs. The implication of these results is discussed throughout the thesis. In addition, a holistic assessment tool, Strategies for Engaged Learning Framework (SELF) is introduced.