The coronavirus disease 2019 (COVID-19) pandemic continues to create tremendous uncertainty in workplaces. Building on a social identity perspective, this study develops and tests a model of how and why COVID-19-associated uncertainty affects employee work outcomes. The model differentiates uncertainty as either internal (job insecurity) or external (perceived environmental uncertainty) to the organization and reveals their different effects on employee organizational identification, which positively affects employee work outcomes (work effort, organizational citizenship behavior, and performance). With a latent change score to model intraindividual changes, we found that increases (or decreases) in job insecurity before versus during the pandemic related to subsequent decreases (or increases) in organizational identification, whereas increases (or decreases) in perceived environmental uncertainty before versus during the pandemic related to subsequent increases (or decreases) in organizational identification; increases (or decreases) in organizational identification then related to increases (or decreases) in positive work outcomes. These findings complement existing theoretical views that uncertainty typically leads to poor performance by inducing anxiety, and that organizational identification suffers during a crisis such as COVID-19. In turn, this research offers practical implications to help organizations avoid discouraging and even encourage greater organizational identification and performance during crises.