Fixturing of components during laser cladding can incur significant conductive thermal losses. However, due to the surface roughness at contact, interfacial conduction is impeded. The effective contact conductivity, known as gap conductance, is much lower than the contacting material conductivities. This work investigates modeling conduction losses to fixturing bodies during laser cladding. Two laser cladding experiments are performed using contrasting fixturing schemes: one cantilevered substrate with a minimal substrate-fixture contact area and one with a substrate bolted to a work bench, with a significant substrate-fixture contact area. Using calibrated gap conductance values, error for the cantilevered fixture model decreases from 20.5% to 6.49% in the contact region, while the bench fixtured model error decreases from a range of 60–102% to 11–45%. The improvement in accuracy shows the necessity of accounting for conduction losses in the thermal modeling of laser cladding, particularly for fixturing setups with large areas of contact.