This paper aims to examine the U.S. property casualty insurer’s loss reserve error in relation to actuaries switching. The results of this paper show that property casualty insurance companies with under-estimated (or over-estimated) reserve error in the previous year are not significantly to switch their actuaries while controlling for organizational structure and corporate governance. The evidence also shows that there is not significant changes in loss reserve error behavior between external (Big 6) and internal (non-Big 6) actuaries switching. We find that stock insurers are more likely to switch their actuaries than mutual insurers. Large Insurers are less likely to switch their actuaries. Insurers with weak financial condition are also less likely to switch their actuaries. We next examine the impact of actuaries switching on future reserve error. We find insurers are less likely to under-estimated reserve error after actuaries switching. In addition, after actuaries switching, stock insurers are more likely to under-estimated reserve error than mutual insurers. Examination of the impact of the Sarbanes-Oxley Act (SOX) on reserve error indicates that insurers are more likely to switch actuaries after SOX. After SOX, insurers with actuaries switching are less likely to under-estimated reserve error and more likely to over-estimated reserve error. The overall results show that reserve error in the previous year does not affect actuaries switching but actuaries switching have impact on insurers’ reserve error in the next year.