We present a sea lion’s (Zalophus californianus) responses to anomalous (unfamiliar) combinations of signs created by reordering, deleting, or adding signs. The sea lion’s responses to these anomalous combinations demonstrated that she had learned a number of syntactic relations from exposure to a limited set of standard combinatorial forms. The learned syntactic relations included two types of conditional relations, (a) sequential conditional relations between sign classes and (b) hierarchical conditional relations between subsets of signs within a combination. The sea lion’s responses also showed that she made little, if any, use of logical or semantic properties of the signs. We propose that the emergence of semantically or logically based syntactic relations may depend on the ability to form stimulus equivalence relations between signs and referents.