NEDD8 is a member of the ubiquitin-like proteins. The overall structure of NEDD8 is quite similar to ubiquitin. Covalent conjugation of NEDD8 to proteins at the post-translational level is called Neddylation. Neddylation occurs similarly to ubiquitination and need enzyme cascades involving E1, E2 and E3. Neddylation has been demonstrated to be essential to maintain the ubiquitin ligase activity of Cullin-Roc based E3 ligases. Compared with the ubiquitination which was widely studied in the past two decades, few substrates were identified for Neddylation and the physiological functions of Neddylation need further investigations. The current progress of function and regulation of protein Neddylation will be reviewed.