The human ERG protein (HERG or Kv11.1) encoded by the human ether-a-go-go-related gene (herg) is the pore-forming subunit of the cardiac delayed rectifier potassium current (IKr) responsible for action potential (AP) repolarization. Mutations in HERG lead to long-QT syndrome, a major cause of arrhythmias. Protein–protein interactions are fundamental for ion channel trafficking, membrane localization, and functional modulation. To identify proteins involved in the regulation of the HERG channel, we conducted a yeast two-hybrid screen of a human heart cDNA library using the C-terminus or N-terminus of HERG as bait. Fifteen proteins were identified as HERG amino terminal (HERG-NT)-interacting proteins, including Caveolin-1 (a membrane scaffold protein with multiple interacting partners, including G-proteins, kinases and NOS), the zinc finger protein, FHL2 and PTPN12 (a non-receptor tyrosine phosphatase). Eight HERG carboxylic terminal (HERG-CT)-interacting proteins were also identified, including the NF-κB-interacting protein myotrophin, We have identified multiple potential interacting proteins that may regulate cardiac IKr through cytoskeletal interactions, G-protein modulation, phosphorylation and downstream second messenger and transcription cascades. These findings provide further insight into dynamic modulation of HERG under physiological conditions and arrhythmogenesis.