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The argon $\cdots$ acrylonitrile $(Ar\cdots CH2CHCN)$ Van der Waals complex has been observed using a pulsed molecular beam Fabry-Perot cavity Fourier transform microwave spectrometer of the Balle-Flygare $type.1$ From the large inertial defect that is observed, the argon is located out of the plane formed by the acrylonitrile subunit by approximately $40\circ$. Two discreet spectra are observed with one being higher in energy than the other by $0.5-1.0cm-1$. The best explanation for the observed spectra is that there is a low barrier to inversion as the acrylonitrile subunit tunnels through a planar configuration of the entire complex. The rotational constants and $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N$ quadrupole coupling constants for the two states are as follows:[FIGURE] Details of the analysis and structure elucidation will be presented.