The present study investigated effects of two hypermedia environments on 95 preservice university teachers' self-regulated learning (SRL) in the context of technological pedagogical content knowledge (TPCK): hypermedia with metacognitive instruction (HYP + META) and without (HYP). The study combined online reflections with self-report measures to assess SRL processes. Results showed that exposure to metacognitive support using the IMPROVE self-questioning method may enhance preservice teachers' ability to reflect on and regulate their learning processes. This, in turn, can develop their TPCK, both as learners (comprehension skills) and as teachers (design skills). Further analysis indicated high correlations within SRL measures (self-reports, online reflections) and between SRL and TPCK tasks. Implications are discussed for teacher training in SRL-integrated TPCK contexts. (Contains 1 figure and 6 tables.)