If the Higgs boson discovered at the Large Hadron Collider (LHC) is not exactly the one in the Standard Model, an alternative mechanism is needed to restore unitarity in the scattering amplitude of longitudinal gauge bosons, and new resonances may appear. This paper presents a search for new heavy neutral resonances (R) produced through vector boson fusion process (ℓ = e, μ) using 3.2 fb−1 of data at √s = 13 TeV recorded by the ATLAS detector at the LHC. No excess above the Standard Model background expectation is observed. Limits are set on the production of five types of neutral resonances with different spin and isospin quantum numbers using a K-matrix unitarization of the vector boson scattering process.