Large climate model uncertainties exist in projections of the Asian Summer Monsoon (ASM). Whereas the El Niño-Southern Oscillation (ENSO) is an important modulator of the ASM, the ENSO-ASM teleconnection is not stable. In addition, teleconnections between ENSO and the East Asian versus South Asian subcomponents of the ASM are distinct from each other. Therefore, understanding the variability of the ENSO-ASM teleconnection is critical for anticipating future ASM intensity. To this end, paleoclimate records can extend the temporal coverage afforded by the instrumental era thousands of years into the past. Recently, data assimilation techniques have been applied for the last two millennia (Last2k), which facilitate physically consistent, globally-gridded climate reconstructions informed by paleoclimate observations. We use these novel data assimilation products to investigate variations in the ENSO-ASM relationship over the last 2000 years. We find that correlations between ENSO and ASM indices are mostly negative in the last 2000 years, suggesting that strong ASM years are often associated with La El Niña events. We also observe a sea surface temperature (SST) pattern in the Pacific that resembles SST anomalies during El Niño events concurrent with century-long periods of weak correlations between ENSO and the East Asian summer monsoon. Additionally, we find a pattern resembling the negative phase of Pacific Decadal Variability during periods of weak correlations between ENSO and South Asian summer monsoon. This study informs our understanding of decadal-scale ENSO-ASM teleconnection behavior and will serve as a baseline for future appraisals of paleoclimate assimilation products.