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Double perovskites BaLaMnSbOwere synthesized by traditional ceramic methods in air as polycrystalline powders. The 0.1 ≤ x ≤ 0.2 compounds belong to the I 2/m monoclinic space group, while the perovskites with x ≥ 0.3 belong to the I 4/m tetragonal space group. The effective presence of mixtures of Mn/Mnhas been well established by X-ray Emission Spectroscopy. BaLaMnSbO(0.1 ≤ x ≤ 0.5) oxides display signs of superparamagnetism in the 40–160 K range, which arises from 3D-nanoclusters formed in regions which are rich in Mn–O–Mnsuperexchange paths originated by the antisite disorder. The analysis of the M vs H hysteresis loops shows that, as x increases, the number of 3D-nanoclusters rises and the number of magnetic ions in the 3D-nanoclusters decreases. The small 3D-nanoclusters cannot sustain magnetic order inside them and this is the reason for the absence of superparamagnetism for x = 0.6 and 0.7. The analysis of the M vs H curves also shows the presence of a weak ferromagnetism which is generated by the canting of the spins in the antiferromagnetic matrix. Neutron Powder Diffraction data reveals that there is long range antiferromagnetic ordering below ≈20 K.