Context :

Aims : The characterization of the stellar population toward young high-mass star-forming regions allows to constrain fundamental cluster properties like distance and age .
These are essential when using high-mass clusters as probes to conduct Galactic studies .

Methods : NGC 7538 is a star-forming region with an embedded stellar population only unearthed in the near-infrared ( NIR ) .
We present the first near-infrared spectro-photometric study of the candidate high-mass stellar content in NGC 7538 .
We obtained H and K spectra of 21 sources with both the multi-object and long-slit modes of LIRIS at the WHT , and complement these data with sub-arcsecond JHK _ { s } photometry of the region using the imaging mode of the same instrument .

Results : We find a wide variety of objects within the studied stellar population of NGC 7538 .
Our results discriminate between a stellar population associated to the H ii region , but not contained within its extent , and several pockets of more recent star formation .
We report the detection of CO bandhead emission toward several sources as well as other features indicative of a young stellar nature .
We infer a spectro-photometric distance of 2.7 \pm 0.5 kpc , an age spread in the range 0.5 - 2.2 Myr and a total mass \sim 1.7 \times 10 ^ { 3 } M _ { \sun } for the older population .

Conclusions :