The infrared spectrum of the ν₁₂ fundamental band of ethylene (C₂H₄) has been measured with an unapodized resolution of 0.004 cm⁻¹ in the frequency range of 1380–1500 cm⁻¹ using the Fourier transform technique. By assigning and fitting a total of 1387 infrared transitions using a Watson's A-reduced Hamiltonian in the I^r representation, rovibrational constants for the upper state (v₁₂ = 1) up to five quartic and three sextic centrifugal distortions terms were derived. They represent the most accurate constants for the band so far. The rms deviation of the fit was 0.00033 cm⁻¹. The A-type ν₁₂ band with a band center at 1442.44299 ± 0.00003 cm⁻¹ was found to be relatively free from local frequency perturbations. The inertial defect Δ₁₂ was found to be 0.24201 ± 0.00002 u Ų.