ObjectiveTo examine longitudinal associations between recent incarceration and subsequent social support among black sexual minority men and transgender women, and whether associations differed between those who did and did not have support prior to incarceration.DesignA secondary analysis in 2020 of data from the HIV Prevention Trials Network 061, a cohort study of black sexual minority men and transgender women recruited in 2009–2010 and followed for 12 months.SettingSix US cities (Atlanta, Boston, Los Angeles, New York City, San Francisco and Washington DC).ParticipantsIndividuals ≥18 years of age who identified as black, reported being male or assigned male at birth, reported ≥1 unprotected anal intercourse event with a male partner in the past 6 months, and reported on incarceration at the 6-month follow-up visit.ExposureHaving spent ≥1 night in jail/prison in the past 6 months reported at the 6-month follow-up visit.OutcomeSocial support measured using a six-item scale assessing frequency of emotional/informational, affectionate and tangible support (range 6–30); and dichotomous indicators of low support for each item (ie, receiving that form of support none/little of the time).ResultsAmong participants who returned for the 6-month visit (N=1169), 14% had experienced incarceration in the past 6 months. Mean support score was 20.9; 18.9 among those with recent incarceration versus 21.2 among those without. Recent incarceration predicted lower support (adjusted β −2.40, 95% CI −3.94 to –0.85). Those recently incarcerated had increased risk of lacking emotional/informational (eg, no one to talk to adjusted risk ratio (aRR) 1.55, 95% CI 1.13 to 2.13) and affectionate (aRR 1.51, 95% CI 1.11 to 2.04) but not tangible support. Effects appeared somewhat stronger among those who had support at baseline.ConclusionsIncarceration may reduce support on re-entry among black sexual minority men and transgender women, populations unequally targeted for incarceration and at risk for low support.