The effective lifetime of the B-s(0) meson in the decay B-s(0) -> J/psi K-S(0) is measured using data collected during 2016-2018 with the CMS detector in root s = 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb(-1). The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the B-s(0) meson invariant mass and proper decay time distributions. The resulting value of 1.59 +/- 0.07(stat) +/- 0.03(syst) ps is the most precise measurement to date and is in good agreement with the expected value.