The top quark pair production cross section $ \left({\sigma}{\mathrm{t}\overline{\mathrm{t}}}\right) $ is measured for the first time in pp collisions at a center-of-mass energy of 5.02 TeV. The data were collected by the CMS experiment at the LHC and correspond to an integrated luminosity of 27.4 pb$^{−1}$. The measurement is performed by analyzing events with at least one charged lepton. The measured cross section is $ {\sigma}{\mathrm{t}\overline{\mathrm{t}}} $ = 69.5 ± 6.1 (stat) ± 5.6 (syst) ± 1.6 (lumi) pb, with a total relative uncertainty of 12%. The result is in agreement with the expectation from the standard model. The impact of the presented measurement on the determination of the gluon distribution function is investigated.