Scatter-hoarding of seeds by animals plays an essential role in seed dispersal of plants and in shaping plant–animal interactions in forest ecosystems, but the function of scatter-hoarding behavior is still unclear. We hypothesize that weak olfactory cues between seeds and scatter-hoarding animals would increase scatter-hoarding. Using a rodent–plant system of Siberian chipmunks Tamias sibiricus and Korean pines Pinus koraiensis, we tested the effects on seed scatter-hoarding intensity by measuring and modifying the seed odor intensities and the abilities of the animals to detect seed odor. Siberian chipmunks seemed to scatter-hoard more seeds with weaker odor signals, and Siberian chipmunks with reduced olfactory ability scatter-hoarded more seeds, supporting our hypothesis. Our studies suggest that olfaction may have played an important role in the evolution of the strength of seed odor and scatter-hoarding behavior of animals, and in shaping plant–animal interactions.