Product and Service Quality Capabilities and Market Performance of the Postal Corporation of Kenya in Western Region 1. Introduction Today, firms operate in highly dynamic environments characterized by constant technological changes and shifts in customer tastes and demands (Ng'ang'a, Namusonge, &Sakwa, 2016). These dynamics necessitate that managers to utilize their internal resources also known as organizational capabilities to fight for survival of the firm (Kamasak, 2017). Rehman, Mohamed &Ayoup (2019) define organizational capabilities as the firm's ability to manage its internal resources effectively, making strategic decisions and effectively implementing the strategic decision process to achieve the desired results. Organizational capabilities are a concept based on Resource-Based Theory that emerged to manage business sustainability and competitiveness (Nayeemunnisa & Gomathi, 2020).Kamasak (2017) advances those organizational capabilities capable of affecting performance include innovation capability, competence of employees' capability, managerial capability, strategic intent & technical capabilities, marketing capability, business processes capability, quality of service and social networks capability.Almutawa, Muenjohn& Zhang (2018) define service quality as an assessment or attitude towards the superiority of a service. As time progresses, service quality can be assessed by looking at the correspondence between expectations and perceptions towards the service performance received by customers, or the service performance provided by the company, judging by the direct assessment given by the customers. Service quality is an emerging competitive dimension in today's business world and identified as one of the strategies of success (Kotler and Keller, 2016). Service organizations, without regards for size, are increasingly seeking the unique ways of differentiating their offering and service quality is one such option in this regard. Many organizations, today, have responded to the strategic and financial impact of quality, treating it as a strategic weapon (Abuzaid, 2015). Product quality is the ability of a