Invasive Prosopis species (Leguminosae) (mesquite) pose a significant threat to biodiversity, pasture production and water resources in South Africa. In an attempt to contain the spread of this noxious weed the South African authorities have supported the introduction of host-specific and damaging seed-feeding biocontrol agents. In order to increase seed losses caused by existing agents, surveys were undertaken in Argentina and a seed-feeding weevil Coelocephalapion gandolfoi Kissinger (Coleoptera: Brentidae: Apioninae) identified. Aspects of the biology and the host range of this seed-feeding weevil were studied in Argentina and South Africa to evaluate its potential as a biocontrol agent. The period from oviposition to adult emergence was c. 40 days. The duration of the stages was: 11–20 days for eggs, 25–40 days for larvae, and 6–16 days for pupae. Field surveys found that the beetle was responsible for 51 % of the seed damage on P. flexuosa. The host range of C. gandolfoi was restricted to Prosopis species in the section Algarobia. Oviposition and feeding preference for Prosopis species native to Argentina and P. glandulosa from North America was very high. We consider C. gandolfoi to be a good candidate for the biological control of invasive Prosopis species in South Africa.