We study second-order hydrodynamic transport in strongly coupled non-conformal field theories with holographic gravity duals in asymptotically anti-de Sitter space. We first derive new Kubo formulae for five second-order transport coefficients in nonconformal fluids in (3 + 1) dimensions. We then apply them to holographic RG flows induced by scalar operators of dimension ∆ = 3. For general background solutions of the dual bulk geometry, we find explicit expressions for the five transport coefficients at infinite coupling and show that a specific combination,H = 2ητ π − 2 (κ − κ * ) − λ 2 , always vanishes. We prove analytically that the Haack-Yarom identity H = 2ητ π − 4λ 1 − λ 2 = 0, which is known to be true for conformal holographic fluids at infinite coupling, also holds when taking into account leading non-conformal corrections. The numerical results we obtain for two specific families of RG flows suggest that H vanishes regardless of conformal symmetry. Our work provides further evidence that the Haack-Yarom identity H = 0 may be universally satisfied by strongly coupled fluids.