Background: Clusterin (CLU) is induced by androgen receptor (AR) pathway inhibition and its overexpression confers treatment resistance. Lipid nanoparticle (LNP) facilitates tumor uptake and intracellular processing through an enhanced permeation and retention effect (EPR), currently with multiple products undergoing clinical evaluation. Gene silencing using small interfering RNA (siRNA) is a promising approach but in vivo delivery remains a major barrier. In our study, we investigated the efficacy siRNA tumor delivery using LNP systems in enzalutamide-resistant (ENZ-R) castration-resistant prostate cancer (CRPC) model. Methods: To validate the effect of LNP siRNA tumor delivery in vivo, gene silencing of a reporter gene, luciferase (LUC), in PC3-M-luc stable cell line was treated with LNP LUC-siRNA and examined for Luc activity by the IVIS imaging system. Next, we investigated the efficacy of LNP CLU-siRNA tumor delivery and LNP CLU-siRNA sensitized AR knockdown activity in ENZ-R CRPC LNCaP in vitro and in vivo models. Results: LNP LUC-siRNA exhibited LUC silencing effects in PC-3M-luc xenograft and metastatic models. LNP CLU-siRNA suppressed PSA and decreased AKT and ERK phosphorylation in ENZ-R LNCaP cells in vitro. LNP CLU-siRNA sensitized AR antisense oligonucleotides (ASO) activity, more potently inhibiting ENZ-R cell growth rates and increased apoptosis when compared to AR-ASO monotherapy. In vivo,combinatory treatment of LNP CLU-siRNA and AR-ASO significantly suppressed tumor growth and serum PSA levels compared to LNP LUC -siRNA (control) and AR-ASO in ENZ-R LNCaP xenografts. Conclusions: The LNP CLU-siRNA systems sensitized AR knockdown resulting in inhibition of ENZ-R LNCaP cell growth, providing pre-clinical proof-of-principle as a promising AR co-targeting approach in ENZ-R CRPC.