Spherical monogenics can be regarded as a basic tool for the study of harmonic analysis of the Dirac operator in Euclidean space R m . They play a similar role as spherical harmonics do in case of harmonic analysis of the Laplace operator on R m . Fix the direct sum R m = R p ⊕ R q . In this paper we will study the decomposition of the space Mn(R m , Cm) of spherical monogenics of order n under the action of Spin(p)×Spin(q). As a result we obtain a Spin(p)× Spin(q)-invariant orthonormal basis for Mn(R m , Cm). In particular, using the construction with p = 2 inductively, this yields a new orthonormal basis for the space Mn(R m , Cm).Mathematics Subject Classification. 30G35, 33C45, 22E70.