High global temperatures will be a great challenge for agricultural production in the near future. Therefore, adaptation of agricultural crops to the high temperatures or development of new heat-tolerant crops with known bioactive compounds is an important strategy for nutritional health and crop improvement programs. In this context, the bioactive compounds of newly developed high temperature-tolerant tomato lines were investigated in terms of lycopene, β-carotene, ascorbic acid and phenolic compounds to assist breeders for the selection of high temperature tolerant tomato varieties with high nutritional quality. Nineteen tomato lines, including control varieties from the “Turkey F1 Hybrid vegetable variety and quality line development” project and the GAP Agricultural Research Institute, were selected for the investigation. Line 11 was superior in lycopene and β-carotene content, while line 18 was superior in ascorbic acid content as compared to control varieties Cansun F1 and Alsancak RN F1. Urfa 2012 and line 28 were found to have the highest numbers of phenolic compounds. Chlorogenic acid, naringenin, trans-ferulic acid and rutin were key phenolic compounds detected in each of the tomato lines. These newly released tomato lines can be used as value-added germplasm or parent sources to develop new heat-tolerant cultivars in breeding programs or as commercial cultivars for their superior functional qualities.