Based on an analysis of around 500 texts from security-affiliated Russian academic journals and one newspaper over a ten-year period, this article details how conspiratorial ideas are spread, tolerated and legitimised within military institutions and official think tanks in Russia. Particular conspiracy theories systematically underpin a broader conspiratorial worldview, which in its basic orientation is anti-Western and illiberal, and which reinforces a perception of Russia as being under threat. As such, this phenomenon serves to justify and rationalise both Russian foreign policy conduct, as well as the targeted repression of various domestic groups as necessary for security reasons. We discuss whether the prevalence of conspiratorial ideas merely reflects an established worldview popular in certain circles or if it influences actual policy and outline some policy implications for the interpretation of Russian foreign policy conduct. The prevalence of conspiracy theories in renowned publications is a concern in itself since it hampers a genuine understanding of international affairs.