We present the first measurement of polarization and CP-violating asymmetries in a B0s decay into two light vector mesons, B0s→ϕϕ, and an improved determination of its branching ratio using 295 decays reconstructed in a data sample corresponding to 2.9  fb−1 of integrated luminosity collected by the CDF experiment at the Fermilab Tevatron collider. The fraction of longitudinal polarization is determined to be fL=0.348±0.041(stat)±0.021(syst), and the branching ratio B(B0s→ϕϕ)=[2.32±0.18(stat)±0.82(syst)]×10−5. Asymmetries of decay angle distributions sensitive to CP violation are measured to be Au=−0.007±0.064(stat)±0.018(syst) and Av=−0.120±0.064(stat)±0.016(syst).