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In general, a mature green tomato will ripen and turn red on the vine or off the vine. Interestingly, an unripe green (UG) tomato also will turn red after being detached from the plant, but the mechanism behind this is unclear. Our study showed that detached UG fruits were able to become red-ripened at the room temperature (25 °C), although fruit quality was lower than that of the vine-ripened fruit. In addition, detached UG fruits exposed to light accumulated more lycopene and total soluble sugars than those incubated in darkness. When the detached UG fruits were stored at a low temperature (10 °C), the fruit-ripening process was nearly blocked, which displayed a non-ripening phenotype. At a high temperature (35 °C), the detached UG fruit showed a yellow-color on ripening, and fruit qualities such as lycopene and soluble sugars were obviously lower than those stored at 25 °C. Moreover, detaching the UG fruit from the plant evoked a rapid increase in total respiration as well as alternative pathway respiration, but ethylene production was not stimulated during the first 24 h of storage. Importantly, the application of nPG, an inhibitor of alternative pathway respiration, markedly suppressed the wound-induced rise in total respiration and delayed the ripening of detached UG fruit. These findings imply that wound-induced respiration might be a signature for launching the onset of the ripening of detached UG fruit, and the optimal conditions of light and temperature are beneficial for the color change and the ripening processes.