In this article, we consider the magnetic corrections to pi-pi scattering lengths in the frame of the linear sigma model. For this, we consider all the one-loop corrections in the s, t, and u channels, associated to the insertion of a Schwinger propagator for charged pions, working in the region of small values of the magnetic field. Our calculation relies on an appropriate expansion for the propagator. It turns out that the leading scattering length, l = 0 in the S channel, increases for an increasing value of the magnetic field, in the isospin I = 2 case, whereas the opposite effect is found for the I = 0 case. The isospin symmetry is valid because the insertion of the magnetic field occurs through the absolute value of the electric charges. The channel I = 1 does not receive any corrections. These results, for the channels I = 0 and I = 2, are opposite with respect to the thermal corrections found previously in the literature.