This paper investigated the effect of big data analytics and its six sub-dimensions on the competitive advantage of healthcare service organisations. Big data analytics have six sub-dimensions: agility capability, data-driven decision making, business intelligence, information technology capability, Internet of Things (IoT) application software, and cloud computing. Big Data Analytics (BDA) refers to the advanced analytical techniques used to process and derive valuable knowledge from large datasets. While BDA has the potential to offer significant business insights and create immense value, many organisations struggle to fully capitalise on their BDA initiatives and gain a competitive advantage. Despite the opportunities presented by BDA, some firms face challenges in effectively leveraging and extracting value from their data analytics endeavours. The study adopted a survey research design. The population of the study comprised 3931 employees of accredited healthcare service firms in Lagos State. The study utilised mixed sampling techniques comprising purposive, proportionate, and random sampling techniques. A sample size of 676 participants was obtained using Cochran’s sample size formula (1977). An adapted questionnaire was used, and an 83.3% response rate was achieved. The Cronbach’s alpha reliability coefficients for various constructs ranged from 0.769 to 0.904. The data were analysed using inferential (regression) analysis. The findings revealed that big data analytics dimensions had a significant effect on competitive advantage (Adj.R2 = 0.937; (F (6, 556) = 0.937), p<0.05). The study concluded that big data analytics affected the competitive advantage of healthcare firms in Lagos State, Nigeria. Based on the findings of the study, it was recommended that the management of healthcare service organisations in Lagos State invest in the combination of Big Data Analytics (BDA) dimensions in order to achieve a long-term competitive advantage. Also, management should use BDA to support the operational activities of the firm to increase cost efficiencies and develop firm-specific BDA knowledge. Keywords: Big data analytics, Healthcare organisation, Competitive advantage, Internet of things application, Information technology capability, Lagos State