  We compute the first-order $\alpha'$ corrections of the non-extremal
Strominger-Vafa black hole and its non-supersymmetric counterparts in the
framework of the Bergshoeff-de Roo formulation of the heterotic superstring
effective action. The solution passes several tests: its extremal limit is the
one found in an earlier publication and the effect of a T duality
transformation on it is another solution of the same form with T dual charges.
We compute the Hawking temperature and Wald entropy showing that they are
related by the first law and Smarr formula. On the other hand, these two
contain additional terms in which the dimensionful parameter $\alpha'$ plays
the role of thermodynamical variable.
