Online retailing is a new but fast growing phenomenon in many countries around the world. The fast pace at which it is growing is resulting in stiff competition on the online market space. Many firms now realise that they cannot only rely on low prices as a source of competitive advantage and are looking for other effective ways of differentiating themselves so as to attract more customers and enhance their satisfaction with their online stores. This paper investigates online store service quality as a source of competitive advantage for online stores. Data was collected from a total of 201 online shoppers from Gauteng South Africa using a structured questionnaire. The findings show that online store service quality as reflected by platform quality, interaction quality and outcome quality has significant influence on customers’ attitude towards online stores as well as their behavioural response in terms of engagement in positive word of mouth. The findings also show that attitude is not a significant mediator of the relationship between online store service quality and customers behavioural response of positive word of mouth. The findings have wide implications of management of online retail stores and these have been highlighted in the paper
