Cows with reduced estrous expression have compromised fertility. This study aimed to determine if the administration of GnRH at AI affects ovulation, progesterone and fertility of cows expressing low estrous behavior. Cows were enrolled at estrus from 3 farms (n = 1629 AI events; Farm A: 757, Farm B: 305, Farm C: 567) and randomly assigned to receive GnRH at AI. Estrous expression was monitored by leg-mounted activity monitors and quantified as the maximum activity occurring at estrus; using the farm median, estrous expression was categorized as high or low. On Farm C, cows were assessed at alert and 7d post alert for ovulation (n = 707) using ultrasonography. On Farm B, ovulation was assessed using plasma samples analyzed for progesterone (P4). A subset of animals were assessed for P4 at estrus and at 7d (n = 526) and grouped using the median. Pregnancy/AI (P/AI) was confirmed at 31 ± 3d post-AI. Outcome variables were tested using GLIMMIX of SAS with estrus as the experimental unit and cow within farm as a random effect. An interaction of treatment and estrous expression on P/AI was found. Without GnRH, cows with higher estrous expression had greater P/AI than those with lower expression, whereas GnRH administration increased P/AI for cows with low estrous expression but not those with high expression (GnRH-High: 46.8 ± 2.5, GnRH-Low: 40.0 ± 2.7; No GnRH-High: 42.3 ± 2.5, No GnRH-Low: 30.8 ± 2.7%; P < 0.01). Cows with high expression had greater P4 7d post-alert (P = 0.04), but not at estrus. There was an interaction of treatment with P4 at alert on P/AI, cows with lower P4 receiving GnRH had greater P/AI than all other groups (GnRH-Low P4: 58.0 ± 4.5, GnRH-High P4: 39.4 ± 4.5; No GnRH-Low P4: 39.9 ± 4.7, No GnRH-High P4: 40.0 ± 4.7%; P = 0.01); this was consistent by estrous expression. Ovulation was not impacted by P4 at estrus but there was an interaction of estrous expression and treatment, where cows with high estrous expression receiving GnRH had greater ovulation rates than all other groups (GnRH-High: 92.0 ± 1.8, GnRH-Low: 85.1 ± 2.0; No GnRH-High: 87.6 ± 1.9, No GnRH-Low: 87.6 ± 2.0%; P = 0.05). In conclusion, fertility of cows with low estrous expression may be increased using GnRH at the time of AI; however, the mechanism behind this relationship is unclear.