The research was carried out to investigate the effect of plant materials which are used as an alternative to synthetic chemicals in organic agriculture (thyme, mint, basil and garlic oil, hot pepper, and neem tree seed extract) and some organic acids (salicylic and jasmonic acid) on the germination, emergence, and seedling traits in broccoli (Brassica oleracea var. italica) cv. Jade. The seeds of broccoli treated with these materials were subjected to germination and emergence tests at 20±1°C and 60±5% RH in autumn period. After that, all seeds (including untreated) were kept at 5±1°C and again evaluated for germination, emergence, and seedling traits in spring period. In spring period, the seeds treated with neem seed extract gave highest germination percentage (91.75%). Also, they germinated in shortest time (3.80 days). The lowest germination/emergence percentage and highest mean germination/emergence time was obtained from the seeds treated with thyme oil in both periods. The seeds treated with basil oil had the higher infected seedlings than others. There were no significant differences among treatments in term of seedling traits (except leaf number).