  A consistent interpretation of the Higgs data requires the same precision in
the Higgs boson masses and in the trilinear Higgs self-couplings, which are
related through their common origin from the Higgs potential. In this work we
provide the two-loop corrections at order ${\cal O}(\alpha_t \alpha_s)$ in the
approximation of vanishing external momenta to the trilinear Higgs
self-couplings in the CP-violating Next-to-Minimal Supersymmetric extension of
the Standard Model (NMSSM). In the top/stop sector two different
renormalization schemes have been implemented, the OS and the
$\overline{\text{DR}}$ scheme. The two-loop corrections to the self-couplings
are of the order of 10\% in the investigated scenarios. The theoretical error,
estimated both from the variation of the renormalization scale and from the
change of the top/stop sector renormalization scheme, has been shown to be
reduced due to the inclusion of the two-loop corrections.
