The twospotted leafhopper, Sophonia rufofascia (Kuoh & Kuoh), is an inadvertently introduced insect that has become a pest in Hawaii’s diverse ecosystems. In this study, laboratory and field experiments were conducted to examine mating, oviposition, and egg and nymphal development of S. rufofascia. In the laboratory at 23 ± 1.5°C, adult S. rufofascia did not mate until 7–9 d after eclosion; the proportion of mating pairs increased from 10 to 100% as age increased from 9 to 15 d. A complete mating process in S. rufofascia consisted of mounting, back-to-back copulation, and postmating rest phases, which lasted for a mean ± SE period of 0.7 ± 0.04, 64.7 ± 1.20, and 3.5 ± 0.39) min, respectively. When caged on individual shoots of host plants (ti, Cordyline terminalis L. and guava, Psidium guajava L.) growing outdoors, adults did not lay eggs until the second week after emergence. The oviposition period lasted 8–9 wk, and the weekly oviposition rate peaked 4–5 wk after emergence (9.8 ± 2.9 eggs per female on ti; 8.1 ± 0.9 eggs per female on guava). There was no significant difference in the total number of eggs laid per female on guava versus ti plants. Under outdoor ambient conditions, eggs of S. rufofascia did not begin to hatch until 4 wk after oviposition, and the peak rate of hatch occurred 6 wk after oviposition. Newly hatched nymphs took a mean of 56.9 ± 2.8 d on guava and 47.2 ± 1.7 d on ti plants to complete development to the adult stage. These results indicate that S. rufofascia may take 3–4 mo to complete a single generation during fall and winter in Hawaii. Because of the 2-mo oviposition period of adults and the large variation in the developmental time of eggs and nymphs, S. rufofascia is likely to have overlapping generations in Hawaii.