Significance: The Milankovitch cycles are orbitally paced variations in insolation that drove periodic climate changes on Earth at the scale of tens to hundreds of thousands years. Longer ‟grand orbital cycles” also exist, but their impacts on paleoclimate dynamics are not well documented for pre-Cenozoic times. Here we tackle this issue by analyzing the stable isotope fluctuations recorded by fossil cephalopods throughout the Jurassic–Early Cretaceous interval. We document a periodicity of ∼9 My in the carbon cycle, except from 190 to 180 Ma when disturbances occurred. This orbital forcing affected carbon transfers by modulating the hydrological processes and sea-level changes. In summary, this ∼9-My orbital cycle is an important metronome of the greenhouse climate dynamics.