Mental health disorders rank among the 10 leading contributors to the global burden of diseases, yet persistent stigma and care barriers delay early intervention. This has inspired efforts to leverage digital platforms for scalable health promotion to engage at-risk populations. To evaluate the effectiveness of a digitally-enabled mental health promotion (DEHP) campaign, we conducted an observational cross-sectional study of a 3-month (February-April 2025) nation-wide campaign in Singapore. Campaign materials were developed using a marketing funnel framework and disseminated across YouTube, Facebook, Instagram, and TikTok. This included narrative videos and infographics to promote symptom awareness, coping strategies, and/or patient navigation to Singapore's Mindline website, as the intended endpoint for user engagement and support. Primary outcomes include anonymised performance analytics (impressions, unique reach, video content view, engagements) stratified by demographics, device types, and sector. Secondary outcomes measured cost-efficiency metrics and traffic to the Mindline website respectively. This campaign generated 3.49 million total impressions and reached 1.39 million unique residents, with a Cost Per Click at 29.33 SGD, Cost Per Mille at 26.90 SGD and Cost Per Action at 6.06 SGD. Narrative videos accumulated over 630,000 views and 18,768 engagements. Overall, we demonstrate that DEHP campaigns can achieve national engagement for mental health awareness through multi-channel distribution and creative, narrative-driven designs.