We find soft X-ray emission lines from the X-ray binary Swift J1858.6-0814 in data from XMM-Newton-RGS: N VII, O VII and O VIII, as well as notable residuals short of a detection at Ne IX and other higher ionisation transitions. These could be associated with the disc atmosphere, as in accretion disc corona sources, or with a wind, as has been detected in Swift J1858.6-0814 in emission lines at optical wavelengths. Indeed, the N VII line is redshifted, consistent with being the emitting component of a P-Cygni profile. We find that the emitting plasma has an ionisation parameter $log(xi)=1.35pm0.2$ and a density $n>1.5times10^{11}$ cm$^{-3}$. From this, we infer that the emitting plasma must be within $10^{13}$ cm of the ionising source, $sim5times10^{7}r_{rm g}$ for a $1.4M_{odot}$ neutron star, and from the line width that it is at least $10^4r_{rm g}$ away ($2times10^{9}(M/1.4M_{odot})$ cm). We compare this with known classes of emission line regions in other X-ray binaries and active galactic nuclei.
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