<p>Smartphone-based chatbot interventions have shown promise in promoting vaccine uptake among South Asian minorities. In this two-arm, cluster-randomised, wait-list controlled trial (Chinese Clinical Trial Registry: ChiCTR2200061503; registration date: June 27^th, 2022), South Asians (aged 18 or older, from Pakistan, India, or Nepal) who had not received influenza or COVID-19 vaccines in the past year were randomly assigned at the cluster level to intervention or wait-list control groups. The intervention comprised a simple rule-based chatbot integrated into the smartphone application and an on-demand feature allowing users to connect with trained research assistants. Among 610 participants analysed, influenza vaccination rates were significantly higher in the intervention group than the control group immediately after (57.8% vs. 1.3%, p &lt; 0.001) and three months post-intervention (68.0% vs. 2.0%, p &lt; 0.001). Our results suggested that smartphone-based chatbot intervention could be an effective strategy to increase vaccination rates among South Asian ethnic minorities.</p>