Is UC Davis more selective than UC San Diego for undergraduate admissions?

Yes. In broad undergraduate admissions terms, UC San Diego is typically viewed as more selective than UC Davis. That is the common perception among applicants and counselors, and it usually shows up in stronger overall applicant demand, especially for high-interest STEM fields. Both are respected UC campuses, but they do not usually sit at the same level of selectivity.

For a student drawn to a large research university with especially intense interest in engineering, computer science, biology, and other STEM-heavy areas, UC San Diego tends to attract a more competitive applicant pool.

UC Davis is still selective and should not be treated as a backup in any casual sense. It appeals strongly to students interested in life sciences, environmental fields, agriculture, veterinary-related paths, public health, and a more traditional college-town setting. In some of those areas, Davis is exceptionally strong, so a student applying to one of its popular programs can still face very tough odds.

If your question is just the broad head-to-head comparison, UC San Diego is the more selective campus overall. If your real concern is your chances, major matters a lot, because the gap can feel bigger in some fields than others.