This study reports the atmospheric pressure viscosity data of liquid 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodooctane, 1-iodononane, 1-iododecane, and 1-iodododecane along with relevant densities of the last five homologues from 253.15 to 423.24 K. It is demonstrated that the atmospheric pressure viscosities of 1-chloroalkanes and 1-iodoalkanes are similar to the (n + 3) and (n + 6) n-alkanes, respectively. At the same time, although the packing fractions of 1-chloroalkanes are most probably similar to the pertinent n-alkanes, in the case of 1-iodoalkanes, such parallels seem to be questionable. Apparently, the latter could explain a success of the entirely predictive modeling framework coupling CP-PC-SAFT with modified Yarranton-Satyro correlation (MYS) [Ind. Eng. Chem. Res. 2015, 54, 6999] in estimating the viscosities of 1-chloroalkanes with the recommended values of critical constants and a desirability of optimizing the experimentally unavailable T-c, and Pc, in cases of 1-iodopropane and further homologues. Besides that, the elevated pressure viscosities of iodoethane exhibit a substantially weaker pressure dependence than the equivalent data of n-octane, which is truthfully predicted by CP-PC-SAFT + MYS. In addition, the residual entropy-based approach of Novak [Int. J. Chem. React. Eng. 2011, 9, A107] predicts the viscosities of both 1-chloroalkanes and 1-iodoalkanes in the less reliable manner than CP-PC-SAFT + MYS. From the fragmental experimental data, an extent of phase splits in the binary systems of 1-iodoalkanes is wider than in the pertinent mixtures of (n + 6) n-alkanes, which is also predicted by CP-PC-SAFT in a reliable manner.