Lentil is now an integral part of prairie cropping systems. Climate forecasts point to variable and increased drought frequency, putting lentil production in jeopardy. Future lentil genotypes will require root systems that can extract more water under drought conditions. This study focuses on root diameter and root tip number, traits known to play an important role in water uptake during drought. We compared the total root length (TRL) in three soil horizons of both wild and cultivated lentil genotypes for three root diameter classes when plants were grown under moderate or severe drought, and when re-watered after exposure to moderate drought conditions. Our study demonstrates that roots of both wild and cultivated lentil genotypes can be categorized into very fine, fine and small diameter classes. Some wild lentil genotypes had significantly higher TRL in the B and C soil horizons when grown under severe or moderate drought and therefore, could act as resources for the transfer of root traits to cultivated lentil genotypes. Further evaluations focused on the root systems of interspecific recombinant inbred lines under drought conditions will be required to determine whether these traits are heritable.