The sex ratio at birth (SRB), defined as the proportion of male to total live births, is a key demographic and biological indicator influenced by both natural and human-induced factors. Studies have reported that stressful events, such as natural disasters, wars, environmental crises, can affect reproductive health and alter SRB. This study investigates the potential impact of an earthquake sequence that struck Sarpol-e Zahab county located in Kermanshah province, Iran, between Aban 1396 and Azar 1397 Hijri Shamsi (HS) (November 2017–November 2018), as well as the behavioral responses of the local population as reflected in online search activity. The area was struck by five earthquakes with magnitude larger than 5 and peak ground acceleration ≥ 200 cm/s² over the course of about a year. Annual birth data of Sarpol-e Zahab county, Kermanshah province and entire Iran from 1390 HS (2011–2012) to 1401 HS (2022–2023) were obtained from the Statistical Centre of Iran. SRB was calculated as the ratio of male to total live births for each year in the 12-year period. Statistical analyses were performed using one-sample T-test to compare annual SRB values with the overall mean. A statistically significant decline in Sarpol-e Zahab SRB was observed in 1398 HS (2019–2020), the year following the earthquake sequence (SRB = 0.506, compared to the 12-year mean of SRB = 0.522, p-value = 0.0004). The reduced SRB was not observed neither in Kermanshah province nor in entire country. The findings indicate that the impact of the earthquake sequence caused an annual SRB decrease in Sarpol-e Zahab in the year following the earthquake sequence.