From a historical and genetic point of view, the Otomi of the Mezquital Valley are a frontier people that have played an important role in the population dynamics of the Mexican Central Plateau. Due to the antiquity of their presence in the area, the Otomi may be bearers of ancient genetic variability, shared mainly today with other groups belonging to the Otomanguean linguistic family and with the Nahua. In this study we analyzed the HLA class II allele frequencies reported in Mexican indigenous populations, in order to provide an intraregional-level historical perspective of the genetic relationships between the Otomi of the Mezquital Valley and indigenous populations from other regions of Mexico. We examined genetic variation in HLA-DRB1 and -DQB1 loci in 66 nonrelated individuals belonging to seven indigenous communities from the Ixmiquilpan municipality in the Mezquital Valley, in the State of Hidalgo, Mexico. The variability of the HLA-DRB1 gene among the Otomi of the Mezquital Valley was mainly concentrated in five alleles: -DRB1^*08:02 (31.06%), -DRB1^*04:07 (25.77%), -DRB1^*14:06 (7.55%), -DRB1^*14:02 (6.06%), and -DRB1^*16:02 (4.55%); these alleles have been previously described in other indigenous populations. The most frequent alleles at the HLA-DQB1 locus were -DQB1^*03:02 (34.09%), -DQB1^*04:02 (31.03%), and -DQB1^*03:01 (19.7%). Furthermore, the HLA-DQB1^*02:02 allele was found in the Otomi group with a frequency of 2.27%; this allele has not been reported in Mexican indigenous populations. In conclusion, the genetic constitution of the Otomi population is intermediate to the northern groups and the genetic variability shared by the peoples of the central regions of Mexico. Furthermore, HLA-DRB1 and -DQB1 allelic variability among the Otomi provides insight into the historical processes implied in the biological admixture with European, Asian, and African populations as well as in the admixture with the population of Mexico City associated with long-standing migratory processes.