Carbon nanotube (CNT) growth has been demonstrated from partially oxidized silicon nanocrystals (Si NCs) that exhibit quantum confinement effects. We determine experimentally and explain with theoretical simulations that the Si NCs morphology together with a necessary shell oxide of ∼1 nm is vital to allow for the nonmetallic growth of CNTs. This contribution is of significant importance to the improvement of nonmetallic catalysts for CNT growth and the development of Si NC/CNT interfaces (ACS Applied Materials & Interfaces 8 (2016) 19012).