A mapped Chebyshev pseudospectral method is developed as an accurate and yet efficient approach to solve unsteady flows. Preserving the conservation laws, the method discretizes a spatial derivative term implicitly while a time derivative term is treated explicitly using the mapped Chebyshev collocation operator. As standard Chebyshev points make the corresponding spectral derivative matrix ill-conditioned due to uneven distribution of the Chebyshev points clustered heavily towards the ends of the interval, an inverse sine mapping function is applied to the Chebyshev collocation operator so that the point distribution becomes more uniform in a time domains and mitigates numerical instabilities correspondingly. Computations of unsteady flows, including onedimensional Burgers' equation and two-dimensional airfoil flows under oscillation and plunging motions, are carried out. Numerical results of the present study are compared with those of the conventional time-marching solution method and the harmonic balance method for each application, and demonstrate high accuracy at much reduced computational cost. The method shows great potential to solve general unsteady flows involving both periodic and non-periodic motions. Nomenclature A = amplitude of oscillation a = Chebyshev coefficient b = Chebyshev coefficient for first differential D = matrix in harmonic balance equation D ch = Chebyshev collocation matrix D T = Chebyshev coefficient matrix D T = Chebyshev coefficient matrix for first differential F = Fourier transform matix G, H = fluxes g = a mapping funtion g' = derivative of a mapping function k c = reduced frequency M = matrix in frequency domain equation M ch = number of reconstruction points by Chebyshev M ∞ = freestream Mach number N hs = number of harmonics p, q = constant of polynomial mapping function Q = conservative variables R = residual T = Chebyshev polynomial T max = time interval t = time V, W = flux Jacobian matrixs in mapped Chebyshev method y = variable of a mapping function α, β = constant of inverse sine mapping function δ, ε = constant of hyperbolic sine mapping function φ = frequency ρ, σ = constant of tangent mapping function