In Argentina, the bacterium Xylella fastidiosa was detected in late 2013 in traditional olive orchards of more than 50 years of age, in the provinces of La Rioja, Córdoba and Catamarca; plants showed marked decline, desiccated branches and apical necrosis in leaves. Olive cultivar Arauco was the most severely affected, whereas the bacterium was detected only in isolated individuals of the cultivar Frantoio. There are few reports of the bacterium in olive, having been reported the subspecies pauca strain CoDiRO (ST53) in Italy, and strain ST16 in Brazil. Multilocus sequence typing (MLST) was used to determine the allelic profile corresponding to this host in Argentina, according to the protocol of Yuan et al. (2010). Amplification of the involved genes was performed from total DNA of infected plants, then PCR products were purified and sequenced. The comparative analysis of the sequences of the seven genes coincided with the sequences of the alleles leuA7, petC6, malF7, cysG9, holC23, nuoL17, and gltT8; the type sequence (ST) 69 was assigned to the obtained allelic profile. Coletta-Filho et al. (2017) obtained the same ST in an analysis of citrus from northeastern Argentina (Misiones and Corrientes). This ST has been found only in Argentina. In Brazil, the strain ST16 is present in olive and coffee, but not in citrus, whereas the hosts of ST69 from Argentina are olive and citrus. The strain CoDiRO from Italy was detected in several hosts (Saponari et al., 2014) but not in citrus.