Growing degree days and photo thermal units accumulation of tomato genotypes as influenced by dates of sowing was studies in Ibadan, south-west Nigeria with the aim of determining the exact duration of different phenophase and their associations with tomato yield determines essential for achieving high yield. Data collected w ere daily minimum and maximum temperatures for estimation of phonological stages growing degree days (GDD), and in combination with daily sunlight duration for estimating phonological stages photo thermal units (PTU), number of leaves per plant over time20, leaf dry weight, stem dry weight and number of fruits per plant at maturity. The result showed that date of sowing plays a major role in the accumulation of GDD and PTU from sowing to maturity of all tomato genotypes. All the genotypes sown a sfirst plant (11/12/08) accumulation highest GDD (77.13)and PTU (910.13) followed by second planting date (18/12/08)with GDD (54.3)and PTU (640) while third planting date (26/12/08)recorded the lowest values of GDD (46.10) and PTU (544.0)respectively. The delay in sowing dates caused a decrease in GDD and PTU requirement of constituent phenophases as well as for the crop duration. Comparison between the genotypes showed that genotype UTC recorded highest GDD (63.8) and PTU (752.73) while GDD (57.63) and PTU (679.9) were the same for Roma VF,UC-82-B and Ibadan local. Thus genotype UTC indicated its longer growth duration as compared to Roma VF,UC-82-B and Ibadan local. The leaf dry matter was significantly (p<0.05)influenced by planting date with first planting date having higher leaf dry matter than second and third planting dates while no significant difference was observed among four genotypes in terms of leaf dry weight. Stem dry weight of the genotypes was statistically significant among the genotypes with first three varieties having higher stem dry weight than fourth. Planting date did not cause any difference in fruit weight per plant likewise the genotypes considered. Finally, the first planting date produced a significantly higher total dry matter than second and third planting dates which was not different stastically. Genotypes Roma VF,UC-82-B and Ibadan local have significantly higher total dry matter than UTC variety.