The concept of self-directedness is a missing link in South African science classrooms, and as a result, science teachers are often not self-directed in employing innovative teaching and learning strategies such as blended problem-based learning (BPBL) that might enhance self-directed learning. Literature is replete with studies showing that science teachers in the United States, Indonesia, and South Africa, to name a few, lack the necessary technological skills to utilise simulations in the teaching and learning of Physical Sciences. This intervention-based explanatory mixed methods study was conducted in one of the nine education provinces of South Africa. Quantitative data were generated using a self-directed learning instrument (SDLI), the Physics Education Technology interactive simulations questionnaire, and a PBL questionnaire. Forty participants were sampled using both cluster and systematic random sampling techniques. Qualitative data were generated through a BPBL scenario, a reflective portfolio, and semi-structured interviews with two purposively selected participants. The quantitative data were analysed using descriptive and parametric statistics. The reflective portfolio was analysed using a performance standards scoring rubric adopted from Smith et al. (2001). The BPBL Scenario Evaluation Schedule and interviews were analysed using Saldaña’s (2013) code-to-theory analytical model. It was concluded that there was a significant difference in participants’ perceptions of PBL, self-directedness, and interactive simulations after attending a teacher professional development intervention (TPDI) and implementing BPBL. The findings show that the utilisation of interactive simulations and PBL in Physical Sciences classrooms were unknown to teachers – suggesting that teachers were not self-directed in implementing BPBL. This study presents a model for designing BPBL activities and an evaluation schedule for assessing those activities for self-directedness in educational practices.