Pragmatic encroachment theories of knowledge may be characterized as views according to which practical factors may partly determine the truth-value of ascriptions that S knows that p – even though these factors do not partly determine S’s belief that p or p itself. The pros and cons of variations of pragmatic encroachment are widely discussed in epistemology. But despite a long pragmatist tradition in the philosophy of science, few efforts have been devoted to relate this particular view to issues in philosophy of science. Consequently, a central aim of the present paper is to consider how the contemporary debates over pragmatic encroachment connect to philosophy of science. More specifically, I will set forth some arguments against the idea of pragmatic encroachment on scientific knowledge. Moreover, I will argue that it is not plausible to respond to these arguments by embedding pragmatic encroachment in the anti-realist framework of constructive empiricism. So, I conclude that there are good reasons to reject pragmatic encroachment theories of scientific knowledge.