Reintroduction is a crucial step in the conservation efforts aiming to restore ecosystems and protect threatened species. However, studies that incorporate and evaluate the effect of plant reintroduction are scarce. A study on a population of Cephalocereus polylophus, a vulnerable cactus endemic to the southern Chihuahuan Desert, allowed us to evaluate the effect of seedling reintroduction on the viability of this population. An integral projection model was used on a 5-year dataset to forecast population size over a century, and to simulate scenarios of seedling survival and protection. The study revealed an asymptotic population growth rate (λ) of 0.97 (95% CI = 0.96 – 0.99). Simulating the seedling survival and an increase in the seedling bank translated into a λ that showed only a slight increase, but remained below one, mainly because the recruitment and survival of small individuals were insufficient to compensate for the population decline. Protecting seedlings against herbivores and increasing their survival to 96.5% resulted in a larger population size (~ 5% average increase) and delayed extinction, in comparison with a no intervention and 60% survival rate scenario. This demonstrates that increasing seedling survival rates through protection and reintroduction efforts can only be conceived as a complementary conservation strategy to those focused on preserving existing individuals. Effective reintroduction strategies can help delay the extinction of the population of this cactus, but the conservation of the current population and its habitat is pivotal for its future survival.