Methamphetamine use and HIV disproportionately affect sexual and gender minority (SGM) people assigned male at birth. Identifying risk factors for methamphetamine use is crucial to inform preventive interventions. In this cohort study with 1,296 SGM people assigned male at birth, ages 16 to 29, and who resided in Chicago, Poisson regression analyses indicated the prevalence of methamphetamine use increased from 2015 to 2023 [Incidence Rate Ratio (IRR) = 1.07; 95% CI = 1.01 to 1.13; = 0.02]. This increase was most pronounced among those ages 25 or older at baseline (IRR = 2.20; 95% CI = 1.33 to 3.63; = 0.002), and 23.9 [Interquartile Range (IQR) = 22.1 to 26.9] was the median age of first-time methamphetamine use. In 826 participants with a prior HIV diagnosis or previous inflammatory measurements, Cox proportional-hazards models examined risk factors for incident, first-time methamphetamine use. Adjusting for other substance use, the rate of incident, first-time methamphetamine use was two-fold greater after HIV diagnosis [adjusted hazard ratio (aHR) = 2.02; 95% CI = 1.27 to 3.23; = 0.003]. For each SD higher C-reactive protein, the rate of incident, first-time methamphetamine use was 18% greater (aHR = 1.18; 95% CI, 1.05 to 1.34; = 0.008). HIV seroconversion and inflammation could increase the risk of initiating methamphetamine use in SGM people assigned male at birth.