Nahdlatul Ulama (NU), the world’s largest Islamic organisation, is renowned for fostering tolerance in Indonesia. However, recent studies have revealed that the degrees of tolerance NU displays are inconsistent, throwing the organisation’s reputation for acceptance into question. By adopting critical juncture and case study analyses, this article finds that tolerance within NU is dynamic for three reasons. First, it evolves depending on the social-political context of the time. Second, NU upholds tolerance within specific limits, extending it to those who do not contradict the Islamic values it upholds and who do not pose a threat to the unitary state of the Republic of Indonesia (NKRI). Third, the commitment to tolerance by NU’s membership, the nahdliyin, varies and does not always align with NU’s principles.