Seed yield is the most important trait for genetic improvement in rapeseed, and it is controlled by quantitative loci/genes. In the present study, QTL mapping for seed yield in rapeseed were conducted at multiple environmental conditions, using a doubled haploid (DH) population derived from a cross between a winter-type cultivar ‘EXPRESS’ and semi-winter-type line ‘SWU07’, and an immortalized F2 population generated by randomly intermating among DH lines. A total of 18 putative QTL were identified in China across two years and 15 putative QTLs were identified in one year in Germany environment. These loci were located on 13 linkage groups including A1, A2, A3.1, A3.2, A7.1, A7.2, A9, C1, C3, C4, C5, C8 and C9, respectively, each of which could explain phenotypic variation ranging from 2.27% to 16.93%. Out of the identified QTL, six loci on linkage groups A2, A3.1, A7.1, A9 and C5 have been detected across environments or populations, thus becoming of interest in controlling seed yield in rapeseed. Collectively, these QTLs provided useful information for future improving seed yield in rapeseed breeding.