Each autumn, American Crows (Corvus brachyrhynchos) in the Central Valley of California, USA, forage heavily on walnut trees (Juglans regia) planted along residential streets. Some of these nuts are dropped onto roads and cracked for immediate consumption, but others are carried away from foraging sites to be cached. I quantified caching behavior to understand its importance in corvid natural history and the potential for corvids to disperse large tree seeds. Crows cached an estimated 2000 walnuts/km²/yr in agricultural fields 1–2 km away. Most (73%) crows that found a walnut left the foraging site with it, and most (77%) of these crows cached their nuts. Some crows carried walnuts long distances (e.g., 5% of nuts foraged from trees were carried >2 km) and buried them in unforested habitat; this indicates that crows may be agents of tree seed dispersal. Transporting and caching a nut required approximately 10 min and increased the likelihood of it being stolen, relative to a nut eaten immediately at the walnut tree. Without knowing the timing and rates of recovery, it is unclear when and to what degree American Crows benefit from walnut-caching, which has not been previously described in this species.