This case study explored the development of two pre-service teachers' subject matter knowledge (SMK) of electromagnetism while integrating the use of concept maps (CM) and collaborative learning (CL) strategies. The study aimed at capturing how these pre-service teachers' SMK in electromagnetism was enhanced after having been taught SMK in a university module on electromagnetism via a lecture mode. The participants' progress in acquiring SMK was monitored when they engaged in individual-constructivist learning and socio-constructivist learning when working in pairs. Data were collected from concept maps on electromagnetism and from individual interviews. This interpretive case study suggests that the participants benefitted in several ways in consolidating their SMK of electromagnetism through integrating CM activities and engaging in CL. These benefits included the revision of previous work; the reflection on choices of the big conceptual ideas in electromagnetism; making appropriate conceptual connections supported by experiments; using new terminology in conceptual linkages; sharing ideas via arguing and explaining to each other; and consolidating learning by drawing and extending concept maps over time. The study suggests that the pre-service teachers did benefit from both the individual constructivist and socio-constructivist approaches in consolidating their SMK through the integrated CL and CM activities.