Abstract This article analyses the failed Dutch Religious Peace of 1578 through the lens of security. As Wayne te Brake recently argued in Religious War and Religious Peace in Early Modern Europe, creating security for all parties is key for an effective religious peace. In the sixteenth century, communal security was deemed a collective responsibility. In practice this meant that religious peace – suppressing and preventing violence and threats between Protestants and Catholics – was framed as a matter of preserving the common peace. Theological questions were dissimulated or kept out of peace settlements. In 1578, the religious peace proposed that Catholics and Calvinists were to live in the Netherlands side by side, each allowed to worship publicly. Some 27 Dutch towns introduced this religious peace. Yet the municipal magistrates mostly did so reluctantly and generally declined to share political power, thus contributing to its failure. Moreover, there were different, conflicting conceptions at work concerning the common peace, as well as regarding how to keep it.