A bstract A search for the production of pairs of heavy Majorana neutrinos (N ℓ ) from the decays of Z′ bosons is performed using the CMS detector at the LHC. The data were collected in proton-proton collisions at a center-of-mass energy of $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV, with an integrated luminosity of 138 fb − 1 . The signature for the search is an excess in the invariant mass distribution of the final-state objects, two same-flavor leptons (e or μ ) and at least two jets. No significant excess of events beyond the expected background is observed. Upper limits at 95% confidence level are set on the product of the Z′ production cross section and its branching fraction to a pair of N ℓ , as functions of N ℓ and Z′ boson masses ( $$ {m}_{{\textrm{N}}_{\ell }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mi>N</mml:mi> <mml:mi>ℓ</mml:mi> </mml:msub> </mml:msub> </mml:math> and $$ {m}_{{\textrm{Z}}^{\prime }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:msub> </mml:math> , respectively) for $$ {m}_{{\textrm{Z}}^{\prime }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:msub> </mml:math> from 0.4 to 4.6 TeV and $$ {m}_{{\textrm{N}}_{\ell }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mi>N</mml:mi> <mml:mi>ℓ</mml:mi> </mml:msub> </mml:msub> </mml:math> from 0.1 TeV to $$ {m}_{{\textrm{Z}}^{\prime }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:msub> </mml:math> / 2. In the theoretical framework of a left-right symmetric model, exclusion bounds in the $$ {m}_{{\textrm{N}}_{\ell }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msub> <mml:mi>N</mml:mi> <mml:mi>ℓ</mml:mi> </mml:msub> </mml:msub> </mml:math> - $$ {m}_{{\textrm{Z}}^{\prime }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:msub> </mml:math> plane are presented in both the electron and muon channels. The observed upper limit on $$ {m}_{{\textrm{Z}}^{\prime }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:msup> <mml:mi>Z</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:msub> </mml:math> reaches up to 4.42 TeV. These are the most restrictive limits to date on the mass of N ℓ as a function of the Z′ boson mass.