Actinyls AnO2 with An = U, Np, and Pu in an expanded porphyrin, alaskaphyrin (AP), are studied by a relativistic density-functional method. The electronic structures of both AnO2 and AnO2AP are investigated by considering all possible low-lying states. To examine the importance of relativity, nonrelativistic calculations were also performed. For UO2 and NpO2, the ground state is altered by the relativistic effects, but it remains unchanged for PuO2. The nonrelativistic ground states of the AnO2AP complexes are all high spin, where the AP highest occupied molecular orbital, b2g, is singly occupied. At the relativistic level, there are two electrons in b2g. The bonding characteristics in AnO2AP are examined by calculations of the AnO2−AP binding energy and charge distribution on AnO2. Other properties such as ionization potentials and electron affinities are also calculated. The predicted spectroscopic constants for NpO2, PuO2, NpO2AP, and PuO2AP would aid in future spectroscopic studies of these molecules.