Abstract Nyctaginaceae are one of the most diverse families in core Caryophyllales. The most diagnostic character of the family is a persistent anthocarp derived from a calyx-like perianth. Anthocarp morphology is highly variable across the family, but its evolution is poorly studied. We investigate anthocarp evolution in Nyctaginaceae through extensive anatomical studies (159 species from 28 genera representing six of seven tribes) and phylogenetic character state reconstructions. We found highly diverse anthocarp anatomy across Nyctaginaceae, with most traits analysed evolving multiple times throughout the family. The representatives of three early-diverging clades of Nyctaginaceae (Leucastereae, Boldoeae and Colignonieae) possess a calyx-like anthocarp with simplified anatomy. The so-called ‘glands’ in Nyctagineae and Pisonieae are emergences, whereas wings originate by accrescence of perianth segments, elongation of the ribs and outgrowths (emergences) of anthocarp mesophyll. Anthocarp anatomy can be considered as a generic-level feature in Colignonieae, Pisonieae, Bougainvilleeae and Nyctagineae. The most dramatic transitions from perianth to anthocarp involve the shrivelling and abscission of the upper perianth part and the maintenance of the basal modified perianth portion that originated in the clade comprising Colignonieae and sister clades.