The poly(ADP-ribose) polymerases (PARPs) catalyze poly(ADP-ribosyl)ation, a post-translational modification of proteins. This consists of the attachment of mono- or poly-adenosine diphosphate (ADP)-ribose units from nicotinamide adenine dinucleotide (NAD+) to specific polar residues of target proteins. PARP1 is the most abundant and best-characterized member of the family of PARP enzymes. PARP1 plays key roles in DNA repair, as well as a wide variety of cellular processes, including transcriptional regulation, chromatin modulation, cellular signaling pathway, inflammation, cellular stress responses and so on. Hence, PARP1 inhibitors have become a promising therapeutic approach for human diseases including cancer. Recent studies indicate that post-translational modifications (PTMs) such as phosphorylation, acetylation, and methylation are crucial for the regulation of PARP1 activity, and dysregulation of modifications on PARP1 is observed in human cancer. In this review, we describe the importance of PTMs to regulate the activity of PARP1, and the involvement of dysregulation of PTMs in human cancer.