Previous studies suggested that epistemically more sophisticated students learned better in a constructivist learning context than epistemically less sophisticated students did. This study further examined if students with "higher" prior epistemic beliefs (EB High) had better learning gains than students with "lower" prior epistemic beliefs (EB Low) in a different constructivist learning context--Knowledge Building. We found that EB High and EB Low students did not differ in learning gains in Knowledge Building. We also examined how EB High and EB Low students engaged in epistemic practices on Knowledge Forum. Through discourse analysis, we found that although EB High students engaged in more sophisticated epistemic practices than EB Low students did, they both improved their epistemic practices; as time unfolded, the gaps between their epistemic practices narrowed down. This study has important implications for how to help students with different epistemic sophistication benefit from a constructivist learning context.