Purpose: There are different types of drivers of adoption of digitalized marketing operations tactics which include firm size, firm readiness, perceived benefits, perceived barriers, customer pressure and competitive pressure. The purpose of this study was to address the relationship between firm size and the adoption of digitalized marketing operations tactics by chain supermarkets in Kenya. Digitalized marketing operations has transformed the retail sectors by providing access to instantaneous, inexpensive contact among sellers, buyers, investors and advertisers anywhere in the world. This has led to traditional marketing and sales strategies becoming less effective in today’s markets.However, there exist a digital divide between consumers and retailers with many retailers failing to leverage the potential of or meet the digital expectations of their customers. This gap between consumers expectation and retail offerings puts at risk more than just shopping revenue that physical store could have earned online, but also poses a serious threat to overall revenue and a challenge to the way they respond to, and anticipate, customers’ shopping habits in-store.
 Methodology: The research study considered the positivism research philosophy and adopted a descriptive research design. The target population of the study was 180 retail chain supermarkets stores in Kenya and all the 180 retail chain supermarkets were included in the sample. The research instrument of the study was a semi-structured questionnaire administered to all the 180 chief operations managers by use of google surveys and/or drop and pick method. The quantitative information was analysed by the help of SPSS program (v.25.0) and Excel.
 Findings: The findings were presented in form of averages, standard deviations, counts and percentages by use of tables. The findings revealed that firm size which include number of employees, number of branches and monthly average customer turnovers (β=0.459, p=0.000) have a positive and significant relationship with the adoption of digitalized marketing operations tactics by chain supermarkets in Kenya. This implies that improvement in 1 unit of the aspects related to firm size improves the adoption of digitalized marketing operations tactics by chain supermarkets in Kenya by 0.253 units.
 Unique Contribution to Theory, Practice and Policy: From the findings, the study recommends the Small and Medium Enterprises (SMEs) in the chain supermarket industry to embrace digital marketing operations tactics and also provide additional support and resources to help them overcome the barriers to adoption. It also recommends creation of awareness among larger firms about the benefits of digital marketing operations tactics, and the potential competitive advantage they can provide. The Diffusion of Innovation theory was validated and provided valuable insights into the factors influencing the adoption of digitalized marketing operations tactics by chain supermarkets in Kenya.