Context : Pismis 18 is a moderately populated , intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc .
Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey .

Aims : New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster .

Methods : Gaia-ESO Survey data for 142 potential members , lying on the upper main sequence and on the red clump , yielded radial velocity measurements , which , together with proper motion measurements from the Gaia Second Data Release ( Gaia DR2 ) , were used to determine the systemic velocity of the cluster and membership of individual stars .
Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only .
Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements .

Results : The average radial velocity of 26 high confidence members is -27.5 \pm 2.5 ( std ) ~ { } km s ^ { -1 } with an average proper motion of pmra = -5.65 \pm 0.08 ( std ) mas yr ^ { -1 } and pmdec = -2.29 \pm 0.11 ( std ) mas yr ^ { -1 } .
According to the new estimates , based on high confidence members , Pismis 18 has an age of \tau = 700 ^ { +40 } _ { -50 } Myr , interstellar reddening of E ( B - V ) = 0.562 ^ { +0.012 } _ { -0.026 } mag and a de-reddened distance modulus of DM _ { 0 } = 11.96 ^ { +0.10 } _ { -0.24 } mag .
The median metallicity of the cluster ( using the six UVES stars ) is [ Fe/H ] = +0.23 \pm 0.05 dex , with [ \alpha /Fe ] = 0.07 \pm 0.13 and a slight enhancement of s- and r- neutron-capture elements .

Conclusions : With the present work , we fully characterized the open cluster Pismis 18 .
We confirmed its present location in the inner disc .
We estimated a younger age than the previous literature values and we gave , for the first time , its metallicity and its detailed abundances .
Its [ \alpha /Fe ] and [ s-process/Fe ] , both slightly super-solar , are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey . Keywords . stars : abundances – open clusters and associations : individual : Pismis 18 – Galaxy : abundances – Galaxy : disk