An angular analysis and a measurement of the differential branching fraction of the decay B 0 → ϕμ + μ − are presented, using data corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions recorded by the LHCb experiment at $$ \sqrt{s}=7 $$ and 8 TeV. Measurements are reported as a function of q 2, the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1 < q 2 < 6 GeV2 /c 4, where precise theoretical calculations are available, the differential branching fraction is found to be more than 3σ below the Standard Model predictions.