Wild type kales (Brassica oleracea var.acephala) and its two mutants which have different petals in number were used as material. One AGL6-homologue from conventional kale varieties denoted as BoaAGL6 was cloned using RACE (rapid amplification of cDNA ends), then expression pattern of BoaAGL6 in each floral organ was examined. The results showed that BoaAGL6 contains a 759 bp open reading frame that encodes a deduced protein with 252 amino acid residues. Phylogenetic analysis indicated that BoaAGL6 belongs to the AGL6-like subfamily. The result from multiple methods (semi-quantitative RT–PCR and quantitative real-time PCR) revealed that the pattern of the expression of BoAGL6 is broader than those of their counterparts in eudicots, with different expression levels in petals, which is high in mutants with the most petals. These results suggest that BoaAGL6 plays important roles in controlling floral organ identity and formation in kale.