This essay traces the evolution of Dutch Calvinists’ attitudes towards Islam in the East Indies. Initially, Calvinists went into the mission field with a dismissive attitude towards Islam, expecting large-scale conversions upon proclaiming the Word of God. After failing to attract a significant number of Muslims, theologians at the universities of Utrecht and Leiden in the mid-1600s undertook comprehensive investigations into Islamic theology in order to better equip pastors overseas. This academic impetus aimed at undermining the authority of the Qur’an through comparative analyses with the Old and New Testaments, which inaugurated a new phase in East Indies missions. To discredit the Qur’an, Calvinist and indigenous linguists worked assiduously to translate biblical texts, culminating in a Malay Bible in 1730. About this time, however, the Calvinist missionary enterprise seemed to run out of steam because of the failure to convert Muslims and because of the VOC’s economic contraction. A number of Calvinist theologians in the Netherlands and pastors in East Asia began to take a rather sympathetic attitude toward Islam, as they regarded religious boundaries as a marker of cultural difference.