Atmospheric rivers (ARs) transport water vapor both regionally and globally as first documented by Zhu and Newell (1994; 1998). They are widely recognized as an important contributor to extreme rainfall, especially over the Western US. The main sources of the water vapor are largely from the tropical ocean where convective systems bring the surface moist flux upward to the troposphere. One such source, the Madden-Julian Oscillation (MJO), has been studied using the RMM index as a measure of the MJO phases based on EOF analysis in connection with ARs (e.g., Zhou et al. 2021, Toride and Hakim 2022). However, a direct analysis of MJO convection as a water vapor source for ARs has not been investigated. This study uses the MJO Large-scale Precipitation Tracking (LPT) by Kerns and Chen (2016, 2020) to examine the direct connection of this water vapor source to ARs. We track both the MJO LPTs and ARs using ERA5 data from 1998-2023. The results provide some new insights into how the MJO affects the water vapor transport in terms of the size, duration, and intensity of the ARs. In general, the ARs associated with the MJO are larger, long-lasting, and carrying more water than those do not. Preliminary analysis of the MJO-AR in relation to extreme rainfall over the western US will also be presented.