A measurement of the B$_{s}^{0}$ decay parameters in the B$_{s}^{0}$ → J/ψϕ channel using an integrated luminosity of 14.3 fb$^{−1}$ collected by the ATLAS detector from 8 TeV pp collisions at the LHC is presented. The measured parameters include the CP -violating phase ϕ$_{s}$ , the decay width Γ$_{s}$ and the width difference between the mass eigenstates ΔΓ$_{s}$ . The values measured for the physical parameters are statistically combined with those from 4.9 fb$^{−1}$ of 7 TeV data, leading to the following: $ \begin{array}{l}{\phi}_s=-0.090\pm 0.078\left(\mathrm{stat}.\right)\pm 0.041\left(\mathrm{syst}.\right)\mathrm{rad}\\ {}\varDelta {\varGamma}_s=0.085\pm 0.011\left(\mathrm{stat}.\right)\pm 0.007\left(\mathrm{syst}.\right){\mathrm{ps}}^{-1}\\ {}{\varGamma}_s=0.675\pm 0.003\left(\mathrm{stat}.\right)\pm 0.003\left(\mathrm{syst}.\right){\mathrm{ps}}^{-1}.\end{array}