Since late 1980’s the banking sector in Pakistan has undergone major structural changes due to financial liberalization and deregulations. This transformation has led to greater competition among financial institutions, favoring in the efficiency and competitiveness of banking sector. As a result, a greater variety and choices of products and services for customers are available while some banking institutions are offering sophisticated delivery systems and more value-added services than rivals. Likewise, banks have also come under enormous pressure to tackle the growing demands and expectations of their consumers as well as due to the shift in customer-centric regulatory paradigm towards protection of financial consumers, posing major challenge for bank to retain existing customers. These considerations converge to imply the need for more specific customer-focused strategies to build and maintain enduring bankclient relationships. Presently, the business environment surrounding banking institution is highly competitive where new clients are hard to attract at mature stage in their life cycles, hence banks must strive for establishing new revenue streams,, particularly in a situation where competition between financial establishments has intensified, banking institutions need to make various efforts to achieve differentiated competitiveness through forging sustainable relationships with customers. In terms of producers of financial services, considering the highly competitive nature of banking industry and increasingly interactive customer roles, fairness in service delivery is essential in developing and maintaining bank-client relationships. Earlier studies show that a consumer''s perception of whether a service provider has fulfilled the obligation to deliver the desired outcome and benefits associated with the service promised to consumers serve as a is a fundamental basis for sustaining and enhancing long-term customer-firm relationships. Service fairness is a multidimensional construct composed of distributive fairness, procedural fairness, informational and interactional fairness, which refers to a consumer’s perception regarding the degree of justice in a service provider’s behavior during service delivery process. Service fairness is an implicit agreement between customers with their service providers to have their needs served well and to be treated fairly according the service outcomes promised. Successful customer relationship management can be attributed to a customer’s positive evaluations of a service provider’s efforts in provision of service fairness excellence during an exchange relationship. Although banking services is recognized to encounter numerous service failure episodes there has been scant investigations in commercial banking sector of Pakistan that addressed the connection among service fairness, relationship marketing and customer engagement. Past studies in the domain relationship marketing strongly support that mutually profitable buyer-seller relationships are key to secure competitive advantage emphasizing the importance of quality and value of relationships. However, there is a lack of an integrative perspective about understanding buyer-seller relationship building process through the lens of service fairness. This research contributes to building a comprehensive understanding on how customer evaluations regarding different facets of service fairness affect bankconsumer relationship building process and lead customers to perform various citizenship behaviors, by examining empirically this relationship at multi-group level. This research study was conducted in Pakistan, using a positivist philosophical lens, data was gathered quantitively with the help of questionnaire distributed using stratified random sampling technique. The validity of survey instrument and structural paths relationships were confirmed using pilot study procedure. The results of pilot survey were very useful in validating the proposed model and measurement scales used in the study however few of the items were dropped from subsequent analysis to improve the reliability and validity of the instrument. Data was gathered from 1740 consumers of banking services located within scheduled bank branches in a single cross-section however only 1430 valid responses were subjected to further analysis. The model was assessed using partial least square based Structured Equation Modeling (PLS-SEM), using Smart PLS 3.2.7 statistical software following the PLS-SEM guidelines proposed by (Jörg Henseler, Hubona, & Ray, 2017) in the field of social sciences research. As a result, the model demonstrated greater predictive response to a consumer’s assessment of service fairness. The results of this research confirmed that banking consumers commonly evaluate fairness in exchange relationships when dealing with service providers. The findings support the model’s structure and indicated that all four dimensions of service fairness determine relationship value and quality, which in turn lead customers to perform citizenship behaviors. The results show that service fairness evaluations also had direct influence on customer citizenship behavior, however this relationship is better explained by a firm’s relationship marketing efforts. This implies that although fair treatment is essential in reinforcing long-term relationships and for customers to engage in citizenship behaviors but it is also a significant condition that may encourage consumers to perform positive extra role behavioral outcomes. Therefore, banks should provide assurance that their services can achieve a sustainable level of favorableness that meets what the service provider has promised to its customers. This study brought to light that the knowledge pertaining to the critical role of service fairness strategies in building valuable, enduring relationships with customers. Moreover, this research contributes in the relationship marketing literature on how service fairness excellence encourage customer to engage in citizenship behaviors in favor of the firm through developing successful long-term mutually beneficial relationship. Therefore, besides service excellence banks need focus on providing excellence in service fairness to create strong relationships with their clients as endured relationship can lead to customer citizenship behaviors.