Abstract Background Over one million children receive treatment for asthma in the UK. South Asian children experience excess morbidity and higher rates of hospitalization than the White population. This study aimed to explore perceptions and experiences of asthma and asthma management in British South Asian and White British families, to identify barriers to optimal management and to inform culturally appropriate interventions to improve management. Methods A qualitative methodology, using semi-structured interviews was adopted. Members of 30 families from six major South Asian ethnic-religious groups were purposively sampled (n = 49). For comparison, 17 White British parents were interviewed. Topics included understandings of asthma; day-to-day management; interactions with health care providers and the perceived quality of healthcare services. Data were analyzed using interpretive thematic analysis, facilitated by NVivo. Similarities and differences between South Asian and White families were analysed across key themes. Results Many of the problems facing families of a child with asthma were common to South Asian and White British families. Both had limited understanding of asthma causes and triggers and expressed confusion about the use of medications. Both groups reported delays in receiving a clear diagnosis and many experienced what was perceived as uncoordinated care and inconsistent advice from health professionals. No family had received an asthma plan. South Asian families had more difficulty in recognising severity of symptoms and those with limited English faced additional barriers to receiving adequate information and advice about management due to poor communication support systems. South Asian parents reported higher levels of involvement of wider family and higher levels of stigma. Attendance at the emergency department was related to previous experience, difficulties in accessing primary care, lack of knowledge of alternatives and difficulties in assessing severity. Conclusions Barriers to optimal asthma management exist at the individual family, community and healthcare systems levels. Culturally sensitive, holistic and collaboratively designed interventions are needed. Improved communication support for families with lower proficiency in English is required. Healthcare professionals need to ensure that families receive an asthma plan and make greater efforts to check families’ understandings of asthma triggers, use of medications, assessment of asthma severity and accessing help.