Kluyveromyces marxianus dairy strains were tested for γ-aminobutyric acid (GABA) production. The genes involved in GABA catabolism (UGA1 and UGA2) and anabolism (GAD1) were found in K. marxianus genome. Their relative expression was evaluated with primer designed ad hoc.Strains were grouped on the basis of GAD1 gene sequence. Representative strains for each group were tested for GABA production by high-performance liquid chromatography. All strains produced it at low levels. qRT-PCR showed the absence of a relation between GABA production and GAD1 gene expression. UGA1 and UGA2 genes were not upregulated and low amounts of succinic acid were detected.All strains released a low amount of GABA suggesting that probably it was stored within cells. The different behaviour of strains in terms of GABA and succinic acid production as well as gene expression highlighted the genetic and phenotypic biodiversity of this species.GABA production and genes involved in its catabolism and anabolism were described in a population of dairy K. marxianus for the first time. The variability observed in terms of genetic and phenotypic biodiversity is important especially to exploit this non-conventional yeast as microbial platform.