Current educational reforms and initiatives are addressing numeracy outcomes for school-age students as a response to concerns regarding their mathematical achievements. In Australia, the Ministerial Council on Education stated, numeracy remains one of the cornerstones of schooling for young Australians (2008). Ultimately, the responsibility for attending to these educational priorities is placed with teachers. Existing literature suggests that student achievement is directly impacted by 'effective teaching' and that effective teaching begins with effective teacher preparation. To address these issues, this pilot study investigated the impact of problem-based (PBL) learning, in a tertiary mathematics education course, on pre-service teachers' mathematics pedagogical content knowledge (PCK) and forms the basis for a larger, subsequent study. To measure pre-service teachers' mathematics PCK, a Mathematics Pedagogical Content Knowledge Instrument was developed. The instrument was delivered pre-semester and post-semester to a control group (n=15) who received traditional, 'lecture-based' instruction, and a treatment group (n=15) who were instructed using the problem-based learning approach. The data were analysed using a paired samples t-test to compare the pre-semester and post-semester means from both cohorts. The findings indicate the treatment group made larger gains in their PCK when compared to the gains in PCK development of the control group. In teaching terms, the findings suggest an intervention such as problem-based learning may enhance the development of pre-service teachers' PCK when compared to using a traditional teaching approach