© 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group. In 1983, the Indonesian government established Pos Pelayanan Terpadu (Integrated Health Post)¿commonly known as Posyandu, an outreach programme for improving mothers¿ and children¿s health, including immunisation. However, child immunisation coverage is still far below national and world targets. There is also wide variation among regions, with low rates found in areas outside Java. This study aimed to explore mothers¿ experiences in immunising their children through Posyandu in East Nusa Tenggara, and West Sumatera, two provinces located outside Java Island. Fifty-three mothers were involved in six Focus Group Discussion (FGDs). The discussions were recorded and transcribed verbatim in the original language. The transcripts were translated into English, coded with Nvivo, and analysed for common themes. This study showed that the success of the immunisation programme through Posyandu relied on the role of community-based health workers. Their ability to integrate with the community increased people¿s trust. This trust encouraged mothers to immunise their children, despite their limited knowledge about immunisation. The other barrier often encountered by the mothers in immunising their children was that the fathers did not allow them to do so. Therefore, collaborative work with the whole community is needed to improve the performance of an outreach programme.