This study assessed the effect of digital marketing strategies namely Social Media Marketing, Search Engine Optimization (SEO), Email Marketing, and Online Advertising on the growth of SMEs in Machakos County. The study was anchored on the Technology Acceptance Model (TAM), which guided the understanding of both social media marketing and SME growth. The Resource-Based View (RBV) supported the SEO dimension, the Diffusion of Innovation (DOI) theory guided the evaluation of email marketing. A descriptive research design was employed, targeting 18,476 registered SMEs. A stratified random sample of 377 respondents was selected, and 340 valid responses were obtained, representing a 90.2% response rate. Data was collected using structured questionnaires, and the reliability of the instrument was confirmed with Cronbach’s alpha values ranging from 0.762 to 0.808, indicating high internal consistency. Quantitative data was analysed using descriptive statistics, Pearson correlation, and multiple linear regression with the aid of SPSS Version 28. The results revealed that all four digital marketing strategies had a significant and positive effect on SME growth. Social Media Marketing emerged as the strongest predictor (β = 0.412), followed by Online Advertising (β = 0.338), Email Marketing (β = 0.286), and SEO (β = 0.319). The model reported an R² of 0.612 and adjusted R² of 0.608, indicating that the four strategies collectively explained 61.2% of the variance in SME growth. ANOVA results further confirmed the model’s significance (F = 51.327, p < 0.05). The study concluded that digital marketing strategies significantly contributed to SME growth by enhancing customer engagement, brand visibility, and profitability. However, challenges persisted, including digital skill gaps, limited access to analytics tools, and constrained marketing budgets. The study recommended that SMEs invest in digital skills training, utilize affordable analytics platforms, and strengthen partnerships with public and private stakeholders to enhance their digital marketing capacity. Future research should explore the role of emerging digital innovations such as artificial intelligence, mobile commerce, and influencer marketing in advancing SME performance across different counties in Kenya.