With decreasing access to facility-based abortion in the US, an increase in self-managed abortion (SMA) using various methods is anticipated. To date, no studies have examined changes in SMA in the shifting policy landscape. To estimate changes in SMA prevalence among the general US population from before to after the Supreme Court's June 2022 decision overturning federal abortion protections. Serial cross-sectional surveys were administered throughout the US from December 10, 2021, to January 11, 2022, and June 14 to July 7, 2023. Participants included online panel members assigned female sex at birth, ages 18 to 49 years (or ages 15-17 years if a household member), who were English- or Spanish-speaking. Year of the survey (2021-2022 vs 2023). Participants were asked whether they had "ever taken or done something on their own, without medical assistance, to try to end a pregnancy" and, if so, details of their experience. Changes in the weighted SMA prevalence between survey years were examined, factors associated with SMA experience were identified, and projected lifetime SMA prevalence was calculated using discrete-time event history models, accounting for abortion underreporting. Median age of the participants was 32.5 (IQR, 25-41) years in 2021-2022 (n = 7016) and 32.0 (IQR, 24-40) in 2023 (n = 7148). Across both years, approximately 14% were non-Hispanic Black, 21% were Hispanic, and 54% were non-Hispanic White. The weighted adjusted proportion that ever attempted SMA was 2.4% (95% CI, 1.9%-3.0%) in 2021-2022 and 3.4% (95% CI, 2.8%-4.0%) in 2023-an increase of 1.0% (95% CI, 0.2%-1.7%; P = .03). Projected lifetime SMA prevalence accounting for abortion underreporting was 10.7% (95% CI, 8.6%-12.8%). In adjusted analyses, SMA experience was higher among non-Hispanic Black (4.3%; 95% CI, 2.8%-5.8%) vs other racial and ethnic (2.7%; 95% CI, 2.2%-3.1%) groups (P = .04) and sexual and gender minority (5.0%; 95% CI, 3.4%-6.6%) vs heterosexual or cisgender (2.5%; 95% CI, 2.0%-2.9%) participants (P < .001). Approximately 4 in 10 (45.3% in 2021 and 39.0% in 2023) SMA attempts occurred before age 20 years. The methods used included herbs (29.8% [2021-2022] vs 25.9% [2023]), physical methods (28.6% [2021-2022] vs 29.7% [2023]), or alcohol or other substances (17.9% [2021-2022] vs 18.6% [2023]). Few participants (7.1% [2021-2022] vs 4.7% [2023]) sought emergency care for a complication. In this serial nationally representative survey study, increased SMA was observed following the loss of federal abortion protections. The findings revealed increased SMA use among marginalized groups, most often with ineffective methods. These findings suggest the need to expand access to alternative models of safe and effective abortion care and ensure those seeking health care post-SMA do not face legal risks.