Unmet need for family planning remains a challenge in Indonesia. The Government has incorporated into the 2020-2024 National Medium-term Development Plan, an ambitious target to reduce unmet need from 12,4% in 2018 to 7.4% in 2024. This will require significant effort, while systematic and updated studies explaining the underlying causes are scarce, especially those that look at the level within the diverse characteristics of Indonesia. This study therefore aimed to investigate the fundamental factors contributing to unmet need for family planning, categorized into five dimensions (D): D.1). weak or ambivalent fertility preferences; D.2). generic disapproval of pregnancy prevention; D.3). method-specific barriers to use; D.4). perceived low risk of getting pregnant; and D.5). partner-related factors. This study also mapped the pattern at the sub-national level namely Java-Bali (region 1/R1), outside Java–Bali 1 (region 2/R2) and outside Java-Bali 2 (region 3/R3). Findings show that the level of unmet need is highest in R3 which consists of provinces that started implementing their family planning program much later than provinces in the other two regions. The study also shows that women between 20-29 years old, with educated husband and larger family size, who consider smaller family size as ideal, are more likely to have unmet need compared to their counterparts in all regions. The likelihood of unmet need is most prominent in the region with the most mature program. The study emphasizes the importance of designing appropriate targeted interventions that are tailored to the local context and not apply a ‘one-size-fits-all’ policy.