The effect of dissipation on quantum reflection is treated in the weak-coupling limit. For high incident energies, dissipation suppresses quantum reflection. Surprisingly, for intermediate incident energies, the reflection rate is greatly enhanced because of energy fluctuations. The reflection rate increases with temperature as exp(${T}^{n}$), with the exponent n dependent on the density of states of the dissipative medium. For low incident energies the problem becomes a strong-coupling problem which we cannot solve.