The biological control of pests is essential for the use of Integrated Pest Management in agricultural environments. In this context, the objective of this study was to identify biological parameters and quantify the parasitism index of Encarsia hispida on Bemisia tabaci biotype B nymphs in cotton plants. The research was conducted at the Entomology Laboratory of the Federal University of Paraíba, in Areia, Paraíba State, Brazil. For the first bioassay, the treatments consisted of cotton cultivars BRS H8 and BRS Topázio to evaluate the biological development of the parasitoid in its host. In the second bioassay, these cultivars were used to assess the impact of the biological agent in a greenhouse. In the first experiment, there were only female parasitoids with longevity of 24.61 and 22.61 days in BRS H8 and BRS Topázio, respectively. However, they were not statistically different. The life cycle of the parasitoid (egg to adult) was 35.68 and 33.71 days in BRS H8 and BRS Topázio, respectively, and they did not differ from each other. In the second bioassay, there were E. hispida parasitism indexes around 34.33 and 29.63% in BRS H8 and BRS Topázio, respectively. The parasitoid E. hispida develops properly when the nymphs of the host were from the two cotton cultivars. The parasitoid E. hispida has an application potential in the biological control of B. tabaci biotype B whiteflies.