Abstract: A diquark model is used to investigate single charmed baryons. In this model, baryon is composed of two diquarks and an antiquark. Masses of lowest lying states with $J^P= 1/2 ^ \pm$ are obtained. Some masses are smaller than other theoretic predictions which indicates that these baryons of pentaquark structure could be relatively stable. The results also show that $Λ(2882)$ may be a pentaquark with $J^P=1/2^-$ and $Ξ(3125)$ may be a pentaquark with $J^P=1/2^+$.