Background The size and weight of tomato seeds depend on genetics and can be modified by environment and management. In some species, a strong relation has been described between physical aspects of the seeds and the quality of the corresponding seedlings, but this cannot be considered a general rule. The objective of this research was to identify any association between the biometric characteristics of tomato seeds and the growth and development of their seedlings. Results A total of 18 lots of hybrid tomato seeds were used (from indeterminate plants with round fruits), belonging to six varieties from two reproduction seasons. Each lot was evaluated for seed size and weight, and seed quality, in terms of the germination test (5 and 14 d after sowing). The number of normal roots emerged with a length above 2 mm was also evaluated at d 3, 4 and 5 after sowing. The length of the seedlings and their total and partial dry weight were measured 5 d after sowing. The results indicate that there was no association between seed size and weight and subsequent seedling emergence, and only weak correlations were found between the dry weight of the radicle and cotyledon and seed size. Conclusion There is little association between the physical characteristics of the seeds and the subsequent seedlings, making it impossible to propose the use of seed weight or size as a compliment to quality evaluation tests.