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Twenty cultivated populations of lucerne (Medicago sativa L) collected from different oasis of Tunisian south were evaluated for morphology and yield. Important among-accessions variation was observed for all traits by variance analysis (length and width of central leaflet at flowering, length and diameter of stem, growth habit, date of flowering, weight of 1000 seed and total fresh and dry matter) when population effect was highly significant (p<0.05) excepted four i.e., stems number, number of smell by inflorescence, number of inflorescences by cluster and plant colour. The large least significant difference at 5% values indicate that a large proportion of this variability can be attributed to genetic variability between individual plants within an accession. Principal component analysis (on three axes represented 59.85% of the total variation) and cluster analysis, based in significant traits, show the distribution of the populations is not according to their geographic origins. Correlation between yield and morphological trait shows that dry matter is negatively correlated to stem length (-0.61) and positively to stem diameter (0.43). Fresh matter was negatively correlated to seed weight (-0.31) and positively to leaf dimension. This work will be completed by a selection programme in these twenty accessions for the improvement of the alfalfa cultivated in the Tunisian south.