<p>By providing daytime structure, Socially Assistive Robots (SARs) can assist older adults in autonomy and mitigate global challenges associated with the ageing society. Despite this potential, SARs are not yet fully integrated into healthcare. Therefore, this research explores the effectiveness of personalisation in communication and language use of SARs, using mass customization and personalised persuasion, to enhance acceptance and perceived persuasiveness of SARs for older adults. The research comprised two studies. Study 1 examined needs in communication and language use of SARs among older adults (N = 6), while Study 2 (N = 33) investigated the impact of mass customization on acceptance and perceived persuasiveness, along with personalised persuasion on perceived persuasiveness and suggestion adoption in a laboratory setting. Study 1 identified six customizable variables, including speech characteristics and the content of messages. Study 2 showed a significant positive effect of mass customization on perceived persuasiveness. Additionally, positive but non-significant correlations were observed between mass customization and acceptance, as well as between personalised persuasion and perceived persuasiveness. Therefore, this study suggests that personalisation through mass customization in SAR communication positively impacts the effectiveness of interventions for older adults. Accordingly, integrating customization in SAR communication may enhance interaction with older adults, addressing healthcare challenges associated with the ageing society.</p>