Using a data sample of proton-proton collisions at √s = 13 TeV, corresponding to an integrated luminosity of 140 fb−1 collected by the CMS experiment in 2016–2018, the B0s → X(3872)ϕ decay is observed. Decays into J/ψπ+π− and K+K− are used to reconstruct, respectively, the X(3872) and ϕ. The ratio of the product of branching fractions BB0s → X(3872)ϕ BX(3872) → J/ψπ+π− to the product BB0s → ψ(2S)ϕ Bψ(2S) → J/ψπ+π− is measured to be 2.21 ± 0.29 (stat) ± 0.17 (syst) % . The ratio BB0s → X(3872)ϕ/BB0 → X(3872) K 0 is found to be consistent with one, while the ratio BB0s → X(3872)ϕ/BB+ → X(3872) K+ is two times smaller. This suggests a difference in the production dynamics of the X(3872) in B0 and B0s meson decays compared to B+. The reported observation may shed new light on the nature of the X(3872) particle.