Saudi students' science academic performance has declined as evidenced by (TIMSS). Saudi science teachers are characterized as using the lecture format without considering individual student differences and failing to provide differentiated Method (DM). This paper reports on an effort to help female Saudi pre-service science teachers (PSST) develop DI knowledge and skills, striving to discern how they understood and practiced differentiation during their field experience after completing a specially-designed DM-focused university course. A mixed method research design followed a sequential, connected approach wherein quantitative data were collected through classroom observations (N=47) using a Likert scale observation instrument followed by qualitative interviews (n=11). The pre and post averages of differentiated teaching skills in the DM planning stage were statistically significant (p=0.0001). The PSSTs moved from very small to moderate mastery on virtually all 10 planning items, from 1.75 to 2.99 on a five-point Likert scale. The DM implementation stage (20 items) also reflected a statistically significant difference with scores moving from 1.68 to 3.01 (moderate mastery). Interview qualitative data confirmed and elucidated the quantitative results. The course was deemed effective in developing PSSTs' differentiated teaching skills (statistically significant, p=0.01). Teaching PSSTs about DM should improve Saudi students' science academic achievement.