We classify \(G_2\) -instantons admitting \(SU (2)^3\) -symmetries, and construct a new family of examples on the spinor bundle of the 3-sphere, equipped with the asymptotically conical, co-homogeneity one \(G_2\) -metric of Bryant–Salamon. We also show that outside of the \(SU (2)^3\) -invariant examples, any other \(G_2\) -instanton on this metric with the same asymptotic behaviour must have obstructed deformations.