This study presents an observation-based, 48-month time series of the vertical structure and strength of the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N, from April 2004 to April 2008. The AMOC had a mean strength of 18.7 ± 2.1 Sv with fluctuations of 4.8 Sv rms. The peak-to-peak amplitude of the seasonal cycle is estimated to be 6.7 Sv, with a maximum in autumn and a minimum in spring. The study reveals that the seasonal variability of the AMOC is dominated by geostrophic midocean and Gulf Stream transports (2.2 and 1.7 Sv rms, respectively), which are larger than the Ekman transport (1.2 Sv rms). A simple model based on linear dynamics suggests that the seasonal cycle is primarily driven by wind stress curl forcing at the eastern boundary of the Atlantic. The seasonal anomalies of the AMOC might represent an important and previously underestimated component of meridional heat transport and storage in the subtropical North Atlantic. Evidence suggests that the observed seasonal cycle is representative of longer intervals, and the long-term decline in the AMOC inferred from hydrographic snapshots between 1957 and 2004 may be partly due to aliasing of seasonal anomalies.This study presents an observation-based, 48-month time series of the vertical structure and strength of the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N, from April 2004 to April 2008. The AMOC had a mean strength of 18.7 ± 2.1 Sv with fluctuations of 4.8 Sv rms. The peak-to-peak amplitude of the seasonal cycle is estimated to be 6.7 Sv, with a maximum in autumn and a minimum in spring. The study reveals that the seasonal variability of the AMOC is dominated by geostrophic midocean and Gulf Stream transports (2.2 and 1.7 Sv rms, respectively), which are larger than the Ekman transport (1.2 Sv rms). A simple model based on linear dynamics suggests that the seasonal cycle is primarily driven by wind stress curl forcing at the eastern boundary of the Atlantic. The seasonal anomalies of the AMOC might represent an important and previously underestimated component of meridional heat transport and storage in the subtropical North Atlantic. Evidence suggests that the observed seasonal cycle is representative of longer intervals, and the long-term decline in the AMOC inferred from hydrographic snapshots between 1957 and 2004 may be partly due to aliasing of seasonal anomalies.