The contagiousness and deadliness of COVID-19 have necessitated drastic social management to halt transmission. The immediate effects of a nationwide lockdown were investigated by comparing matched samples of New Zealanders assessed before (Nprelockdown = 1,003) and during the first 18 days of lockdown (Nlockdown = 1,003). Two categories of outcomes were examined: (a) institutional trust and attitudes toward the nation and government and (b) health and well-being. Applying propensity score matching to approximate the conditions of a randomized controlled experiment, the study found that people in the pandemic/lockdown group reported higher trust in science, politicians, and police, higher levels of patriotism, and higher rates of mental distress compared to people in the prelockdown prepandemic group. Results were confirmed in within-subjects analyses. The study highlights social connectedness, resilience, and vulnerability in the face of adversity and has applied implications for how countries face this global challenge. (PsycInfo Database Record (c) 2020 APA, all rights reserved).