This article looks into the dangers posed by the return of the North Caucasus militants in Syria and Iraq to the security of the Russian Federation. The article first divides the recruitment of North Caucasian foreign fighters in Syria and Iraq into two distinct waves. I argue that the first wave of North Caucasus foreign fighters (2011–2013) chose Syria because they could not fight in the North Caucasus. By contrast, the second wave (2014–2016) openly decided not to fight in their own region, preferring to join an international jihadist front. I then build on the literature about the impact of foreign fighters on domestic insurgencies to analyse the potential impact of these returnees on the regional insurgency in the North Caucasus. I identify four factors conditioning the motivations to return and returnee impact on domestic insurgency: a favourable context for return, an existing network in the region, resonance of the militants’ ideology with the local population, and the will to return to the region. I argue that the greater threat will come from the field commanders from the Second Chechen war exiled in Syria, rather than the more numerous second wave foreign fighters integrated into ISIS.