We classify G 2 -instantons admitting S U (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 S U (2) 3 -invariant examples, any other G 2 -instanton on this metric with the same asymptotic behaviour must have obstructed deformations.