Xenotoca doadrioi differs from other congeners of the Xenotoca eiseni group and other Xenotoca species occurring in the Pacific Coast drainages by the combination of the following characters (none unique to the species): females with 14 dorsal rays (vs. 15 or 16 in X. melanosoma and 13 in X. lyonsi), 14 anal fin rays (vs. 5 or 16 in X. melanosoma), 12 pectoral fin rays (vs. 13 in Xenotoca eiseni), 8 caudal peduncle scales (vs. 9 in Xenotoca eiseni and X. melanosoma), 32 scales in a lateral series (vs. 31 in Xenotoca lyonsi), and 10 suparorbital pores (vs. 9 in Xenotoca eiseni and X. lyonsi). Females of X. doadrioi have large caudal peduncle (standard length/end of the anal fin-hypural plate distance = 3.8, vs. 4.1-4.2 in X. eiseni and X. lyonsi) and SL/end of dorsal fin-hypural plate distance = 3.6 (vs. 3.9-4.2 in X. eiseni and X. lyonsi), large eye (Head length/Eye Diameter = 3, vs. 3.5-3.7 in X. eiseni and X. lyonsi). Males possess 14 dorsal rays (vs. 15 or 16 in X. melanosoma and 13 in X. lyonsi), 14 anal fin rays (vs. 15 or 16 in X. melanosoma), 12 pectoral rays (vs. 13 in Xenotoca eiseni), 8 caudal peduncle scales (vs. 9 in Xenotoca eiseni and X. melanosoma), 11 transversal scales (vs. 9 in X. lyonsi), 32 scales in a lateral series (vs. 31 in Xenotoca lyonsi) and 10 suprorbital pores (vs. 9 in Xenotoca eiseni and X. lyonsi). It has a smaller head (Head Length/Head High = 1.4, vs. 1.1-1.2 in Xenotoca eiseni and X. lyonsi), the body is less high (Standard Length/pelvic-pectoral fin distance = 4.7 vs. 4-4.4 in Xenotoca eiseni and X. lyonsi) and large caudal peduncle (Standard length/ end of the anal fin-hypural plate distance = 3.8 vs. 4-4.2 in Xenotoca eiseni and X. lyonsi), and standard length /end of dorsal fin-hypural plate distance 3.8 (vs. 4.1-4.3 in Xenotoca eiseni and X. lyonsi) (Ref. 117630).