Drought is one of the major environmental factors limiting crop production in the world. In order to evaluate some physiological and biochemical traits of rapeseed varieties (Brassica napus L.) under drought stress, a field experiment was conducted as a split plot, arranged in a Randomized Complete Block Design (CRBD) with three replications at the end of flowering to seed filling (26 days). The main factor was drought stress in two levels including stress and control (160 and 80 mm evaporation from pan, respectively) and the sub-factor was cultivar at three levels including (1) Billy, (2) Adriana and (3) Tassilo. Relative water content, stomatal conductance, proline and total sugar content were measured 7, 12 and 26 days after the cessation of irrigation. The results showed drought stress at flowering stage (7 days after stress) reduced the relative water content, stomatal conductance and increased total sugar and proline content. Stress at pod setting stage (12 days after stress) and seed filling (26 days after stress) reduced the relative water content and stomatal conductance and increased proline and total sugar content. Seed yield and its components were measured after plant maturity. Stress at flowering stage reduced seed yield and its components but reductions in seed weight were not significant. The highest and lowest seed yield was observed in Adriana in control treatments (2814 kg.h^-1) and in Tassilo in stress conditions (994.4 kg.h^-1), respectively. According to the results, Adriana showed a better performance under drought stress than other cultivars. Thus, cultivation of this cultivar is recommended in arid areas.