In a modern and increasingly complex society, students are expected to acquire skills and knowledge to deal with societal challenges, for example, climate change. These include scientific reasoning competencies (SRC), which describe abilities to solve scientific problems by applying scientific skills and knowledge and thus play a crucial role in science education. To foster SRC, science teachers are expected not only to possess these competencies themselves but also to be aware of how their students acquire SRC and have instructional strategies to teach SRC. Preservice science teachers should already have acquired this pedagogical content knowledge (PCK) on a basic level by the time they graduate from university. To investigate this development of PCK about SRC in initial teacher education, we conducted an exploratory study with a sample of 36 preservice science teachers in a Master of Teaching program at a public university in Victoria, Australia. We used the PCKSR-bio, a multiple-choice instrument for assessing PCK for different scientific reasoning activities regarding biology-related classroom situations. We did not find differences between the PCK about SRC of preservice science teachers in the first year of their master's studies and those in the second year of their master's studies, which indicates that their level does not significantly increase during the first year of their Master of Teaching program. An analysis of the participants' responses to the items revealed that they had comparable knowledge regarding each of the scientific reasoning activities addressed and were best at answering questions that addressed students' misconceptions. This is relevant for teachers who supervise early-career teachers as they should know what knowledge early-career teachers bring with them from initial teacher training and what they still need to learn. Furthermore, a comparison between the preservice science teachers in Australia and the preservice biology teachers in Germany, both in a similar phase of their initial teacher education, revealed that the participants in Germany achieved a significantly higher average test score than the participants in Australia. The findings are discussed and recommendations for the improvement of science teacher education related to SRC and potentially for in-service professional development are made.