Bellazzini, BrandoRiva, FrancescoSerra, JaviSgarlata, Francesco2019-03-252019-03-252019-01-20https://openscience.sissa.it/handle/1963/35333We construct the effective field theory for a single massive higher-spin particle in flat spacetime. Positivity bounds of the S-matrix force the cutoff of the theory to be well below the naive strong-coupling scale, forbid any potential and make therefore higher-derivative operators important even at low energy. As interesting application, we discuss in detail the massive spin-3 theory and show that an extended Galileon-like symmetry of the longitudinal modes, even with spin, emerges at high energy.enPreprint