The functions of an employer brand are to attract and retain employees. Previous research on incumbent employees has typically focused on commitment related variables; therefore, it remains unclear whether working for an attractive employer motivates incumbent employees to engage in their work. The purpose of the present study was to investigate the process in which organizational attractiveness leads to employee engagement. Drawing from both signaling and self-determination theory, this study proposes that organizational attractiveness will lead to employee engagement through autonomous motivation. It is also proposed that this relationship would be dependent upon whether the incumbent employee experiences perceived organizational support. Employees (n = 220) from various firms across North America were recruited and surveyed online at two time points. Organizational attractiveness and its dimensions positively predicted employee engagement and autonomous motivation. It was also found that autonomous motivation mediates the influence of organizational attractiveness on employee engagement; whereas the effect appears to be moderated by perceived organizational support. Results showed support for the mediation-moderation model. However, different patterns emerged for the moderating effect of perceived organizational support. It is concluded that brand value dimensions along with organizational support interact to motivate incumbent employees to engage in their work. Theoretical and practical implications are discussed.