Effects of frequency of prescribed burning on invertebrate abundance, diversity, and biomass were investigated in a shortgrass prairie encroached by mesquite, Prosopis glandulosa Torr., at Cross Bar Management Area in Potter County, TX. Invertebrates were collected from three burn treatments (frequencies of 2–3, 4–6, and 8–12 years) by using pitfall traps in 2007 and 2008. Analysis of variance was used to compare abundance, diversity, and biomass at the order and family levels using fire frequency, season, and year as main effects. In general, the season and year had more effect on abundance, diversity, and biomass than did burn frequency. These patterns are consistent with the idea that weather has more impact than fire on invertebrate biomass in shortgrass prairie. Longer-term monitoring of the effects of fire frequency is necessary to better elucidate long-term effects of burning on invertebrate communities in mesquite-encroached shortgrass prairie.