The study aimed to investigate the level of pedagogical content knowledge (PCK) and its patterns of development, the level of professional performance (PP), and the level of self-efficacy beliefs (SEB) of female new science teachers in light of a number of categorical variables: preparation programs, years of experience, classes taught by the teacher, GPA, and level of professional development (PD). The study also aimed to investigate the relationship between each of the levels of PCK, PP and SEB. The mixed approach with the design of triangular mixed methods (QUAN-QUAL) was used in a longitudinal descriptive survey. The population of the study consisted of (209) science teachers and (580) second-field teachers, from the governorates of: Muscat, Al Dakhiliyah, and South Al Batinah. The study sample consisted of (n=38) novice teachers whose years of experience ranged from the year of employment to five years, and the study was implemented throughout the academic year (2019/2020). Data were collected by means of instruments which were used to quantify the qualitative data such as lesson plans analysis, classroom observations and interviews. The PCK scale was built and consisted of (36) indicators, and its psychometric properties have been verified. In addition, the study used Danielson Educational Framework Scale (Danielson, 2007/2013) was used to measure the level of (PP). Also, the study used the Science Teaching Efficacy Beliefs Instrument Form B (STEBI-B) (Riggs & Knochs,1990), and the stability of both scales was calculated by the (Cronbach's alpha) coefficient with a value of (0.90) and (0.71) respectively. In order to determine the patterns of development of PCK, the study used the interrelated model of teacher professional growth (IMTPG) as an analytical tool for qualitative data extracted from lesson plans, notes and interviews, according to the design of Strauss and Corbin for the grounded theory (Strauss and Corbin, 1990/1999). The results of the study revealed a statistically significant change (p < 0.05) in the level of PCK of female new science teachers throughout the academic year, and a statistically significant interaction (p < 0.05) between the change in the level of PCK and the level of PD. The results also showed that the simple development pattern of PCK is the most common and frequent among new science teachers throughout the three measurements, followed by the complex development pattern. In addition, there were no statistically significant differences (p ˃ 0.05) in the patterns of development of PCK during the different measurement stages attributed to all the categorical variables, except for the variable of classes taught by the teacher in the second measurement only (p < 0.05). Also, the study concluded that the PCK can be developed among new science teachers as a result of specific mechanisms of knowledge exchange between the three types of PCK (Personal, Enacted and collective PCK) within the domains of professional growth of the teacher (external, personal, practice and output) in the context of science teaching and learning. The study also showed that there was no statistically significant change at the probability value (p ˃ 0.05) in the level of PP of female new science teachers throughout the school year, and there were no statistically significant interactions at the level of significance (p ˃ 0.05) for the change in the level of PP with all the categorical variables. In addition, the level of the new science teachers' SEB was high in the general level of the scale, and its sub-levels: self-efficacy beliefs and teaching output expectations beliefs. Furthermore, there were no statistically significant differences in the level of SEB among the new science teachers due to the categorical variables, except for the PD level variable (P<0.025). Finally, the results showed that the level of PCK is positively high and statistically significant (P<0.05) with the PP (β = 0.56) with the level of SEB remaining constant, and there is a statistically significant positive medium correlation (P<0.05) between SEB and PP (0,31=β) with the level of PCK remaining constant, and the linear combination of the level of PCK and SEB explains (48%) (Adjusted R2 = 0.45) of the variance in the level of PP of new science teachers. Considering the findings of the study, a set of recommendations and suggestions were introduced including: raising new science teachers' awareness about their PCK and how to integrate its components to support students in learning science, educating them about the mechanisms for developing their PCK in their professional context, and encouraging them to conduct action research and discussion among colleagues to enhance their PCK, PP and SEB. Also, the study suggested conducting a similar longitudinal study to investigate the PCK with its components: content knowledge, knowledge of students' understanding in science, knowledge of instructional strategies and representations and knowledge of assessment of science learning and knowledge of the way they integrate among them. Furthermore, the study suggested conducting a comparative study of the development of PCK among novice and expert teachers with similar professional context. It also proposed designing a training program based on the principles of the theory of the development of PCK and studying its impact on the PP and SEB of science teachers and the academic achievement of students.