Introduction Asthma is one of the most common long-term conditions worldwide. Mass media can influence public perceptions of asthma and its treatment, yet there is limited literature on how online media portrays asthma and asthma treatment. The aim of this study is to explore the portrayal of asthma and inhaled treatments in online mass media in New Zealand.Methods Documents available between 2014 and 2019 were retrieved from national patient support organisations and online news outlets. Documents were screened for inhaler images and mentions of two or more keywords relating to asthma. Asthma medication manufacturers were contacted to access direct-to-consumer advertisements. A coding instrument was developed to quantitatively analyse the retrieved documents.Results In total 124 documents were retrieved and analysed; 59 from patient support organisations and 65 from online news websites. No online direct-to-consumer advertisements were retrieved. Using inhalers was the most frequently cited asthma management strategy (84%, 84/100). Metered dose inhalers were the most common inhaler device (78%, 175/225) portrayed or mentioned and blue was the most common colour (48%, 109/225). Under half (45%) of metered dose inhalers were shown with a spacer. Online press items contained more emotive themes such as challenge, fear, and stigma content than resources from patient support organisations.Conclusion Blue-coloured metered dose inhalers, traditionally associated with relievers, were the most commonly depicted devices in New Zealand online mass media. Most online news articles used emotive language when discussing asthma and asthma treatments, while patient support organisations used more objective language. How media influences public perceptions of asthma and its treatment needs to be considered by health promoters.