Objective Low-income and minority adolescents are at high risk for poor asthma outcomes, due in part to adherence. We tested acceptability, feasibility, and effect sizes of an adherence intervention for low socioeconomic status (SES) minority youth with moderate- and severe-persistent asthma. Design and Methods Single-site randomized pilot trial: intervention (n = 12; asthma education, motivational interviewing, problem-solving skills training, 1 month cell-phone with tailored text messaging) versus control (n = 14; asthma education; cell-phone without tailored messaging). Calculated effect-sizes of relative change from baseline (1 and 3 months). Results Intervention was judged acceptable and feasible by participants. Participants (12–18 years, mean = 15.1, SD = 1.67) were 76.9% African-American, 80.7% public/no insurance. At 1 and 3 months, asthma symptoms (Cohen’s d‘s = 0.40, 0.96) and HRQOL (PedsQL™; Cohen’s d‘s = 0.23, 1.25) had clinically meaningful medium to large effect sizes. Conclusions This intervention appears promising for at-risk youth with moderate- and severe-persistent asthma.