We study the effect of viscosity on the thermal transfer at the interface associated with a spherical liquid droplet impulsively started at constant velocity in another liquid of large extent at rest. Exact solutions for the thermal distributions are derived at short moving time. From algebraic and numerical considerations we show that viscous effects on the thermal transfer at the interface are negligible by comparison with the inviscid solutions. On the contrary, they predominantly occur on both side of it, in the two adjacent boundary layers, with a spreading effect with time. (C) 2003 Elsevier Science Ltd. All rights reserved.