Context : Knowledge of the abundance distribution of star forming regions and young clusters is critical to investigate a variety of issues , from triggered star formation and chemical enrichment by nearby supernova explosions to the ability to form planetary systems .
In spite of this , detailed abundance studies are currently available for relatively few regions .

Aims : In this context , we present the analysis of the metallicity of the Gamma Velorum cluster , based on the products distributed in the first internal release of the Gaia-ESO Survey .

Methods : The Gamma Velorum candidate members have been observed with FLAMES , using both UVES and Giraffe , depending on the target brightness and spectral type .
In order to derive a solid metallicity determination for the cluster , membership of the observed stars must be first assessed .
To this aim , we use several membership criteria including radial velocities , surface gravity estimates , and the detection of the photospheric lithium line .

Results : Out of the 80 targets observed with UVES , we identify 14 high-probability members .
We find that the metallicity of the cluster is slightly subsolar , with a mean [ Fe/H ] = - 0.057 \pm 0.018 dex .
Although J08095427-4721419 is one of the high-probability members , its metallicity is significantly larger than the cluster average .
We speculate about its origin as the result of recent accretion episodes of rocky bodies of \sim 60 M _ { \oplus } hydrogen-depleted material from the circumstellar disk .

Conclusions :