Despite an elevated mortality rate from lethal interactions with humans, the North Atlantic right whale population has continued to grow during the first decade of the new millennium. This unexpected population growth is the result of a 128% increase in female-specific reproduction relative to the 1990s. Here, we demonstrate that the recent increase in annual right whale calf production is linked to a dramatic increase in the abundance of its major prey, the copepod species Calanus finmarchicus, in the Gulf of Maine. The resurgence of C. finmarchicus was associated with a regime shift remotely forced by climatic changes in the Arctic. We conclude that decadal-scale variability in right whale reproduction may be largely driven by fluctuations in prey availability linked to climate-associated ecosystem regime shifts.