The gene encoding the aquaporin-2 water channel is regulated transcriptionally in response to vasopressin. In the renal collecting duct, vasopressin stimulates the nuclear translocation and phosphorylation (at Ser552) of β-catenin, a multifunctional protein that acts as a transcriptional co-regulator in the nucleus. The purpose of this study was to identify β-catenin interacting proteins that may be involved in transcriptional regulation in rat inner medullary collecting duct (IMCD) cells using both experimental and computational approaches. We used a standard chromatin immunoprecipitation procedure coupled to mass spectrometry (ChIP-MS) in a nuclear fraction isolated from rat IMCD suspensions. Over four biological replicates, we reproducibly identified 43 β-catenin binding proteins, including several known β-catenin binding partners as well as novel interacting proteins. Multiple proteins involved in transcriptional regulation were identified (Taf1, Jup, Tdrd3, Cdh1, Cenpj and several histones). Many of the identified β-catenin binding partners were found in prior studies to translocate to the nucleus in response to vasopressin. There was only one DNA-binding transcription factor (TF), specifically Taf1, part of the RNA-polymerase II pre-initiation complex. To identify sequence-specific TFs that may interact with β-catenin, Bayes' Theorem was used to integrate data from several information sources. The analysis identified several TFs with potential binding sites in the Aqp2 gene promoter that could interact with β-catenin in the regulation of Aqp2 gene transcription, specifically Jun, Junb, Jund, Atf1, Atf2, Mef2d, Usf1, Max, Pou2f1 and Rxra. The findings provide information necessary for modeling the transcriptional response to vasopressin.