Abstract: Background and Objectives: Tomato is worldwide one of the most consumed fruit due to its nutritional and potentially health promoting properties. However, these properties can be influenced by many factors including bioregulators, biofertilizers and biopesticides. Since extracts/fractions from leaves of Polyscias fulva (P. fulva), Cupressus lusitanica (C. lusitanica), Tephrosia vogelii (T. vogelii), Senna spectabilis (S. spectabilis) and Callistemon viminalis (C. viminalis) are well known for their effects on plant grown and development, the present study was carried out to verify whether they could influence tomato seeds germination and seedlings growth through biochemical changes. Materials and Methods: Aqueous and methanol extracts were obtained by macerating the leaf powder into water and methanol, respectively. Methanol extracts were then partitioned into hexane, ethyl acetate and residual fractions. About 10 tomato seeds were treated with these extracts and fractions sprouted in 90 mm diameter petri dishes. After 15 days of experiment, the seedlings were harvested and some of their biochemical parameters were studied. Results: Treatments of tomato seeds with extracts and fractions resulted globally in an increase in total phenol and protein contents and in radical scavenging activity of seedling extracts. This was particularly true with P. fulva, T. vogelii and S. spectabilis extracts. Methanol extracts from all the five plant species, whatever the concentration, significantly (p<0.001) stimulated phenol synthesis in tomato seedlings. Furthermore, there was significant (p<0.05) increases in radical scavenging activities of tomato seedling extracts (RSa50 varying from 4.57-8.53) after treatments of tomato seeds with methanol extracts. The fractionation of the methanol extract better concentrated the antiradical activity in hexane fraction as compared to ethyl acetate and in some extent to residual fractions. Except for methanol extract, best stimulatory effect on protein/phenol synthesis and radical scavenging activities in tomato seedlings was observed at low concentration (0.156 mg mL–1). Conclusion: These results showed that the tested plant extracts and fractions can influence some biochemical parameters in tomato seedlings. The results obtained in this work can be useful for tomato crop protection and production.