Whilst there is no doubt that extremely high dissolved iron concentrations on the order of 10-100 nM are observed in oxygen minimum zones overlying shallow waters proximal to shelf sediments, the temporal variability in such concentrations is poorly defined due to a reliance on snapshot cross-shelf sections to study trace metal distributions. However, multiple cruise campaigns since the 1980s have studied iron dynamics over the Peruvian shelf, particularly between 9-17°S where the shelf is broad, extremely productive and known to feature benthic dissolved iron effluxes which are amongst the highest measured globally. By combining data from 11 cruises during 1984-2017, including 4 new unpublished campaigns, we are able to ascertain controls on dFe dynamics on interannual timescales. High dFe concentrations (>10 nM) are confined to a narrow shelf region within 50 km of the coastline, where iron concentration is also most sensitive to the El Niño–Southern Oscillation index. The shelf iron was low during El Niño events (< 20 nmol/L) and was relatively high with a wider range of variability during La Niña event (upper layer: 4.43-34.31 nmol/L; deep layer: 2.88-52.07 nmol/L). Elevated Fe concentrations are always associated with sedimentary inputs under low oxygen conditions. In northern Peru, considering shifts in Fe concentration alongside Chl-a and a coastal upwelling index, changes in dFe concentration in surface layer (above 20 m) were potentially a more significant driver of interannual variability in Ch-a in Peru than upwelling.