Heat conduction in single-walled carbon nanotube (SWNT) aerogels is investigated by an off-lattice Monte Carlo method. Thermal boundary resistances (TBRs) between the SWNT and four permeated gases of argon, nitrogen, neon and hydrogen are reported from fitting simulation results with experimental data. It is found that the TBRs between the SWNT and the permeated gases decrease with larger gas molecular masses. Effects of volume fractions and complex morphologies of SWNTs on thermal conductivities of SWNT aerogels are also quantified. The effective thermal conductivities of SWNT aerogels increase with the larger volume fraction, the greater length and the smaller diameter of the SWNTs. (C) 2015 Elsevier B.V. All rights reserved.