Abstract: Parent selection, determining combining abilities and genetic variation are important in breeding programs. Diallel crosses, therefore, were tested among six canola varieties (Foseto, Option 500, Goliath, Kristina, Shiralee and PF-7045.90). Thirty hybrids and six parents were planted in a lattice design with 3 replications at Mazandaran Agricultural Researches Center, 2004-2005. Primary analysis of variation showed significant differences between genotypes; hence it seemed possible to study the desired traits through diallel analysis. Results of analysis of variation as per Griffing,s 1st method for the duration of 50% of germination, 50% of emergence, three leaf stage, four leaf stage, the time between three and four leaf stage, primary length of root, length of seedlings and seedling vigor index showed that there were significant differences between genotypes (p<0.01). Mean square of general and specific combining ability and reciprocal crosses, statistically were significant for all traits, but mean square of reciprocal crosses for primary length of root was not significant. Mean square (GCA)/mean square (SCA) ration in all traits was significant owing to additive and non-additive gene effects of above mentioned traits, but non-additive gene effects are more important. Estimation of degree of dominance more that one for traits of studied and low narrow heritability showed that non-additive gene effects plays an important role in genetically control of these traits. Heterosis for all traits was negatively significant. Over all it could be concluded that, cv. Shralee was the best parent and KristinaxShiralee was the best cross for all seedling traits.