  The LHCb Collaboration announced the observation of doubly charmed baryon
through $\Xi_{c c}^{++} \rightarrow \Lambda_{c}^{+} K^{-} \pi^{+} \pi^{+}$ in
2017. Since then, a series of studies of doubly heavy baryons have been
presented. $\Xi_{cc}^{++}$ was discovered through nonleptonic four-body decay
mode, and experimental data has indicated that the decay modes of $\Xi_{c
c}^{++}$ are not saturated by two and three-body intermediate states. In this
work, we analyze the four-body weak decays of doubly heavy baryons
$\Xi_{cc}^{++}, \Xi_{cc}^+$, and $\Omega_{cc}^+$. Decay amplitudes for various
channels are parametrized in terms of SU(3) irreducible amplitudes. We point
out that branching fractions for Cabibbo-allowed processes
$\Xi_{cc}^{+}\to\Lambda_c^+\pi^+ \pi^0 K^-$,
$\Omega_{cc}^{+}\to\Lambda_c^+\pi^+ \overline K^0 K^-$ would be helpful to
search for $\Xi_{cc}^+$ and $\Omega_{cc}^+$ in future measurements at
experimental facilities like LHC, Belle II, and CEPC.
