The first spectroscopic study of the argon-diacetylene complex is reported here. The rotationally resolved near infrared spectrum has been analyzed in terms of a conventional asymmetric rotor Hamiltonian, yielding a set of ground and vibrationally excited state rotational constants consistent with a "T-shaped" geometry, similar to that of Ar-C2H2. Using distributed potential parameters determined previously for the Ar-C2H2 system we have developed an empirical potential for Ar-C4H2. A ground state calculation using this potential and the collocation method gives a vibrationally averaged structure in good agreement with experiment. A tentative assignment is also made for the band origins of the Ar-2, Ar-3-diacetylene complexes.