Although different types of gender-based violence (GBV) have been documented in disaster-affected populations, no studies have documented a quantitative increase in rates of GBV among populations living in protracted displacement after a disaster. We aimed to assess the change in rates of GBV after Hurricane Katrina among internally displaced people (IDPs) living in travel trailer parks in Mississippi. The study design included successive cross-sectional randomized surveys, conducted in 2006 and 2007, among IDPs in Mississippi using a structured questionnaire. We sampled 50 travel trailer parks in 9 counties in Mississippi in 2006, and 69 parks in 20 counties in 2007. A total of 420 female respondents comprised the final sample. We measured respondent demographics, forms of GBV including sexual and physical violence further subtyped by perpetrator, suicidal ideation, suicide attempt, and Patient Health Questionnaire-9-assessed depression. Respondents had a mean age of 42.7 years. The crude rate of new cases of GBV among women increased from 4.6/100,000 per day to 16.3/100,000 per day in 2006, and remained elevated at 10.1/100,000 per day in 2007. The increase was primarily driven by the increase in intimate partner violence. GBV experience was significantly associated with increased risk for poor mental health outcomes. Overall, the rate of GBV, particularly intimate partner violence, increased within the year following Hurricane Katrina and did not return to baseline during the protracted phase of displacement. Disaster planning efforts should incorporate plans to decrease the incidence of GBV following a disaster, and to ensure adequate services to people with postdisaster GBV experience.