Infrared spectra of Ar–C2D2 are observed in the region of the ν3 fundamental band (asymmetric C–D stretch, ≈2440cm−1) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Transitions are assigned involving K=0–2 in the ground vibrational state, and K=0–4 in the excited state. The intermolecular bending combination band is also observed, giving a bending frequency of 4.798cm−1. Despite this low bending frequency, the Ar–C2D2 spectrum qualitatively resembles that of a normal semi-rigid molecule, in contrast to He– and Ne–C2D2 which are much closer to the limit of free internal rotation.