BACKGROUND: Despite Canada’s provision of universal health coverage, socioeconomic barriers to good-quality health care remain. Asthma provides an appropriate case study given its high prevalence, availability of effective controller therapies, and known variations in care. OBJECTIVES: The aim of this study is to examine the extent of differences in the economic burden of asthma and indicators of guideline-based care across socioeconomic status (SES) gradients. RESEARCH DESIGN: A total of 29,283 adults with moderate to severe asthma were identified from British Columbia’s administrative health data for the year 1997-2013 and were matched to adults without asthma on the basis of sex and age. Direct medical costs (in 2013 Canadian dollars, $) included all-cause inpatient, outpatient, and pharmacy costs. SES was measured at individual (receiving social assistance) and aggregate (median neighborhood household income) levels. We assessed the impact of SES on excess direct costs of asthma (the difference in all-cause direct medical costs between an asthma patient and the matched individual), and on use of asthma controller versus reliever medications. Associations were evaluated using generalized linear models. RESULTS: Asthmatics receiving social assistance incurred $706 (95% confidence interval, $302-$1014) higher annual excess costs than the rest of the sample. Annual excess costs were $120 ($18-$168) higher in low-SES versus high-SES neighborhoods. Low SES, at both individual and aggregate levels, was consistently associated with lower expenses on controller medications and higher expenses on reliever medications, indicators of suboptimal asthma care and control. CONCLUSION: Even under universal health care, individuals in lower SES groups did not receive guideline-based asthma care, potentially explaining their higher costs.