Guava (Psidium guajava) and araçá (Psidium spp.) plants are important for the Brazilian economy, as their fruit is both accepted by the consumers, and makes a beneficial contribution to the human diet thanks to their content in vitamin C, carotenoids and phenolic compounds. Here, we report the content in the fruit of free ascorbic acid, lycopene, β-carotene, flavonoids and phenolic compounds, and the total antioxidant activity present in a collection of guava and araçá accessions curated at the Embrapa Semiarido germplasm bank. Guava fruits with a red-coloured pulp flesh contained a significant amount of carotenoids, especially lycopene, and a high concentration of phenolic compounds. These compounds were largely responsible for the antioxidant activity of the araçá accessions. Among the guava accessions, phenolic compounds were also responsible for the antioxidant activity. High levels of free ascorbic acid were present in most accessions. In both guava and araçá, there is substantial potential to develop cultivars with a good level of consumer acceptability.