This study sought to determine the impact of coronavirus disease 2019 stay-at-home (SAH) and reopening orders on trends and types of firearm violence in California, Ohio, and the United States, hypothesizing increased firearm violence after SAH. Retrospective data (January 1, 2018, to July 31, 2020) on firearm incidents/injuries/deaths and types of firearm violence were obtained from the Gun Violence Archive. The periods for SAH and reopening for the US were based on dates for California. Ohio dates were based on Ohio's timeline. Mann–Whitney U analyses compared trends and types of daily firearm violence per 100,000 legal firearm owners across 2018-2020 periods. In California, SAH and reopening orders had no effect on firearm violence in 2020 compared with 2018 and 2019 periods, respectively. In Ohio, daily median firearm deaths increased during 2020 SAH compared with 2018 and 2019 and firearm incidents and injuries increased during 2020 reopening compared with 2018, 2019 and 2020 SAH. In the United States, during 2020, SAH firearm deaths increased compared with historical controls and firearm incidents, deaths and injuries increased during 2020 reopening compared with 2018, 2019 and 2020 SAH (all P < 0.05). Nationally, when compared with 2018 and 2019, 2020 SAH had increased accidental shootings deaths with a decrease in defensive use, home invasion, and drug-involved incidents. During 2020 SAH, the rates of firearm violence increased in Ohio and the United States but remained unchanged in California. Nationally, firearm incidents, deaths and injuries also increased during 2020 reopening versus historical and 2020 SAH data. This suggests a secondary “pandemic” as well as a “reopening phenomenon,” with increased firearm violence not resulting from self-defense. •Defensive forms of firearm violence decreased in the US during SAH.•Ohio had increased firearm deaths during SAH, whereas California did not.•Nationally there was increased firearm violence during the reopening, suggesting a “reopening phenomenon”.