Physiological basis of genetic variability in drought response and its association with yield and related indices is not clear in Brassica. In this study 36 accessions belonged to seven species of Brassica were evaluated under normal, moderate and severe stress environments. Physiological traits along with seed yield, seed yield components, oil content and two selection indices (stress tolerance index, STI and drought susceptibility index, DSI) were studied. Moderate and intense stress caused reduction in seed yield and the most studied traits. Based on the STI, B. carinata and B. juncea were identified as the superior species in moderate stress condition while B. oleracea was the most tolerant under intense stress. Moderate drought stress significantly increased the ratio of chlorophyll a to chlorophyll b (Chla/Chlb) while severe stress decreased it. Although relative water content (RWC) had positive correlation with STI, its heritability was low. Chlorophyll content (TChl) was associated with STI and had moderate heritability. Positive correlation was found between proline content and DSI under both stress conditions. Results showed large variation is among studied species for drought tolerance and related traits indicating that selection in this germplasm would be useful. Changes in chlorophyll content can be recognized as a key component affecting drought tolerance in Brassica.