Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is an important pest of crucifers distributed along different climatic regions across the world. To understand the effect of elevated temperatures on the survival rate and development of diamondback moth on cauliflower, an experiment was conducted evaluating six different temperatures (31, 32, 33, 34, 35 and 36°C) in Open Top Chambers during 2019- 2020. Survival and longevity were recorded at daily intervals. Results revealed that the total life cycle of P. xylostella was longest at 31°C and it declined with increasing temperatures. However, P. xylostella did not complete its development at 35 and 36°C. Fifty percent mortality was observed after 24.4 days at 31°C, after 22.6 days at 32°C, and after 14 days at 34°C. Increasing temperatures significantly reduce the survival rate of P. xylostella, but temperatures above 34°C were found to be lethal affecting the growth and development of P. xylostella. The most probable reason for the incomplete development of the insects at higher temperature was the inability of the larvae to consume adequate nitrogen to support the temperature dependent development rate.