This research offers a blueprint for how a cross-species comparative approach can be realized empirically. In a single design, parallel procedures and instruments were used in 2 species, dogs (Canis familiaris) and humans (Homo sapiens), to test whether personality differences exist and can be judged in dogs as accurately as in humans. Personality judgments of humans and dogs were compared on 3 accuracy criteria: internal consistency, consensus, and correspondence. Results showed that, on all 3 criteria, judgments of dogs were as accurate as judgments of humans. These findings are consistent with the evolutionary continuity hypothesis and suggest an important conclusion not widely considered by either personality or animal researchers: Personality differences do exist and can be measured in animals other than humans.