Much has been made of the threat of battle hardened jihadis from Islamist insurgencies, especially Syria. But do Americans who return home after gaining experience fighting abroad pose a greater risk than homegrown jihadi militants with no such experience? Using updated data covering 1990–2017, this study shows that the presence of a returnee decreases the likelihood that an executed plot will cause mass casualties. Plots carried out with American returnees from Islamist insurgencies abroad also decrease the likelihood that a plot will come to fruition. The presence of a known foreign fighter increases the likelihood of detection and disruption by law enforcement officials. These data also show successful attacks by any but lone-actors are becoming increasingly rare. However, attacks planned and executed by close-family members are the exception to the general rule.