A semi-similar solution of an unsteady mixed convection flow over a rotating cone in a rotating viscous fluid has been obtained when the free stream angular velocity and the angular velocity of the cone vary arbitrarily with the time. Both the prescribed wall temperature and the prescribed heat flux conditions are considered in the present investigation. The non-linear coupled partial differential equations governing the mixed convection flow have been solved numerically using an implicit finite difference scheme in combination with the quasi-linearization technique. Numerical results are presented for the skin friction coefficients, Nusselt number and Sherwood number. The effects of various parameters on the velocity, temperature and concentration profiles are also reported here. (C) 2003 Elsevier Ltd. All rights reserved.