We have devoloped a completely analytical equation of state for the long-range triangular-well (LR-TW) fluid of variable well width (2≤λ≤4) as a function of temperature and density based on the augmented van der Waals theory. Hard spheres with a short-range Yukawa attraction are used as the reference fluid. We present the vapour-liquid coexistence curve and thermodynamic properties such as pressure and internal energy. Comparison with computer simulation data and the first- and second-order Barker-Henderson perturbation theory results are discussed. © 2011 Taylor & Francis.