In order to understand if and how employer branding influences employees' work behaviours and enhances employees' ability to contribute to organizational productivity, effectiveness, and competitiveness, one needs to examine its functionality and capacities beyond that of employee attraction and retention to that of employee development, engagement, and performance. This research aims to do that by answering the following questions:1. What are the factors present in the content and delivery of employer brand promises and how might they influence employee performance?2. What influence does employees' perceived level of employer brand promise fulfilment by their organization have on their level of organizational citizenship and task performances?A mix method case study was conducted on one of Canada's best-of-the-best employers. In total, 19 managers were interviewed and 316 employees were surveyed.Five themes emerged to reflect the employer brand promise content factors that could influence performance. They are the factors of personal sustainability, personal connectedness and belonging, opportunities and growth, personal stake and influence, as well as significance and esteem. Three themes emerged to reflect the employment benefit materialization factors. They are brand championship, branding control, and stakeholder selection and interaction. Quantitative results suggest that as a whole, statistically significant, positive, and generally weak to moderate influence exists between employees' perceived level of employer brand promise fulfillment and their organizational citizenship performance. The influence on task performance is much weaker. However, there is stronger indication that employees' perceived fulfillment of employer brand promises positively influences their perception of 1) their employment experience as being desirable and distinctive, 2) their organization as being a great place to work, 3) their happiness to spend the rest of their career at the organization, and 4) their lack of frequency in thinking of leaving the organization, and these positive perceptions, in turn, further influence employees' organizational citizenship and task performances.