Introduction and objectives: Asthma is a chronic and heterogeneous disease that affects people of all ages and has a high estimated increase in prevalence worldwide. Asthma control represents a main goal in the disease management. International studies revealed low levels of disease control resulting in a significant burden for healthcare systems, not only in terms of quality of life, but also in terms of health costs. Modifiable and non-modifiable factors have been identified as relating to poor asthma control level. In this study we evaluated the distribution of asthma control levels in Portuguese adult population and examine the determinants associated with uncontrolled asthma. Materials and methods: Using a similar methodology to the one employed in the Asthma Insights and Reality in Europe (AIRE) survey, 327 active asthmatic patients were identified by random phone number and completed a questionnaire during 2011 to 2012. Asthma control was assessed by the evaluation of GINA based symptom control, by Asthma Control Test™ (ACT) and by self-perception of control. To examine the relationship between uncontrolled asthma and its determinants, univariate logistic regression analysis, sequential multivariable regression and population attributable risk percentage were determinate. Results: 35.2% active asthmatic patients had uncontrolled asthma, 64.8% partially controlled and none of the individuals had total control of asthma assessed by ACT test. Factors significantly associated with poor asthma control scores were: age (OR 1.02 per year of age; 95% CI: 1.01–1.03), female sex (OR 1.87; 95% CI: 1.15–3.04), educational level (OR 0.5; 95% CI: 0.28–0.89 at high school level or over), occupation (OR 4.92; 95% CI: 2.12–11.42 if looking for a first job or unemployed) (OR 2.51; 95% CI: 1.35–4.65 if being retired), income (OR 0.23; 95% CI: 0.07–0.72 if >619 euros), BMI (OR 1.09 per BMI unit; 95% CI: 1.03–1.14), having rhinitis symptoms (OR 4.40; 95% CI: 2.56–7.58) and using inhaled corticosteroids (OR 0.44; 95%CI: 0.24–0.82 if used in the past or never used). Looking for a first job or being unemployed, BMI and having rhinitis symptoms remained significant after multivariate adjustments. Conclusions: Uncontrolled asthma was associated with several determinants. Their identification can contribute to improve asthma care both from clinical and from public health perspectives.