Multipath delays and signal outages in urban environments have been the most difficult problems in Global Navigation Satellite System (GNSS)-based cooperative vehicular navigation systems. In this paper, we develop a non-line-of-sight (NLOS) GNSS signal detection algorithm and propose a multipath-resistant hybrid sum-product algorithm over a wireless network (MRH-SPAWN) and multipath-resistant hybrid cooperative extended Kalman filter (MR-hcEKF) techniques that significantly enhance multipath robustness in urban environments, compared with H-SPAWN and hcEKF, respectively. We provide theoretical derivation and realization of the proposed techniques and demonstrate the performance with numerous Monte Carlo simulations using field measurements of multipath delays. The proposed techniques significantly improve the positioning accuracy of all vehicles and outperform the conventional cooperative positioning (CP) technique in urban multipath environments.