Background <p>Equitable healthcare access is a key aspect of health equity, yet migrants face substantial barriers. In Malaysia, migrant workers encounter structural and socio-economic barriers to healthcare. Acculturation and social support may influence healthcare utilisation, but their interrelated role remains unclear. This study examined associations between acculturation, social support, and healthcare utilisation among Indonesian migrant workers in Malaysia, and whether social support was indirectly associated with the relationship between acculturation and healthcare utilisation.</p> Method <p>A cross-sectional study was conducted in the Klang Valley, Malaysia, from October 2024 to February 2025. Acculturation was measured through language proficiency and social interaction, and social support through friends, family, and third parties. Outpatient healthcare utilisation was self-reported. Associations were analysed using partial least squares structural equation modelling (PLS-SEM).</p> Results <p>Among 322 respondents, 22.7% utilised outpatient healthcare services, mainly at private facilities with substantial out-of-pocket costs. Language proficiency was associated only with support from friends (β = 0.198, <i>p</i> = 0.016), while social interaction showed no association with social support. Social support showed no significant direct or indirect association with outpatient healthcare utilisation. Social interaction was negatively associated with outpatient healthcare utilisation (β = -0.165, <i>p</i> = 0.019). Age (β = 0.154, <i>p</i> = 0.005), length of stay (β = 0.278, <i>p</i> = 0.008), and undocumented status (β = -0.361, <i>p</i> = 0.005) were significantly associated with outpatient healthcare utilisation.</p> Conclusion <p>Acculturation and social support showed limited associations with outpatient healthcare utilisation, as structural barriers remain substantial. Inclusive policies are needed to improve equitable healthcare access among migrant workers.</p>