A central task in efforts to identify pathways to ecologically and socially sustainable economies is to reduce inequality and poverty while reducing material consumption, which has recently inspired future post-growth scenarios. We build a model to explore the potential of a universal basic income (UBI) to serve these objectives. Starting from the observation that post-growth trajectories can take very different forms we analyze UBI in two scenarios advanced in the literature. Comparing UBI in a "local self-sufficiency" economy to a UBI in an "automation" economy, we show that although both scenarios satisfy central sustainability criteria, the impact of a UBI would differ greatly between these contexts. Our analysis shows that a UBI is less compatible with a labor-intensive local self-sufficiency economy than a capital-intensive, high tech economy. We conclude that the feasibility and attractiveness of a UBI in a post-growth scenario depends greatly on the specific characteristics of the economy.