Abstract
This study examines the relationships between social media marketing, e-service quality, payment security, and purchasing decisions among Indonesian SMEs. A quantitative approach was employed, utilizing structured online questionnaires distributed through purposive sampling to 459 executives and senior managers of SMEs in Indonesia. Data were analyzed using Structural Equation Modeling (SEM) with SmartPLS 4.0. The measurement model evaluation confirmed strong reliability and validity across all constructs, with Cronbach's Alpha and Composite Reliability values exceeding 0.70 and Average Variance Extracted (AVE) above 0.50. The findings demonstrate that social media marketing has a positive and significant influence on purchasing decisions (β = 0.279, t = 2.101, p = 0.016), enabling businesses to reach wider audiences, build trust, and foster engagement. E-service quality exhibits a positive and significant influence on purchasing decisions (β = 0.766, t = 2.777, p = 0.000), indicating that superior online service quality increases consumer purchase likelihood. Payment security also positively influences purchasing decisions (β = 0.289, t = 2.681, p = 0.010), as consumers demonstrate greater confidence and willingness to transact when they perceive adequate security measures. The R² value of 0.654 indicates substantial explanatory power of the model, while Q² values above zero confirm satisfactory predictive relevance. These findings suggest that trust in transaction security can significantly enhance consumers' probability of making purchases in the digital era. The phenomenon of payment security carries significant implications for Small and Medium Enterprises (SMEs), where guaranteed security can increase revenue and customer trust, while security risks may lead to financial losses and data breaches.