Objective: Uncontrolled asthma is associated with higher risk of hospital admissions and death. Low adherence to inhaled corticosteroid (ICS), the cornerstone of asthma therapy, is well-documented. Our aim was to investigate if hospital admission with an acute exacerbation of asthma changes ICS adherence. Methods: This retrospective cohort study comprises 241 patients hospitalized with an asthma exacerbation over 12 months (May 2019–April 2020). The primary outcome was proportion of ICS adherent patients, defined as Medication Possession Ratio (MPR) ≥80%, in the six-month period before and after admission. Results: The pre- to post-admission proportion of ICS adherent patients increased from 10% to 13% (p = 0.25) and the mean ICS MPR increased from 34% to 42% (p < 0.001). Different patterns of post-discharge adherence were observed, as adherent patients remained adherent, while patients with poor pre-admission adherence increased their adherence during two months after discharge followed by a decline in MPR. Co-variates such as sex, age, body mass index (BMI), GINA 2020-treatment step did not predict improvement in adherence after discharge. Conclusions: Admission with an asthma exacerbation did not increase the proportion of patients adherent with controller medication, primarily ICS. Although an improvement in adherence was initially seen primarily in previously poorly adherent patients, this increase was transient as it decreased over time post-discharge.