BackgroundMental ill health has a high economic impact on society and employers. National and international policy advocates line manager (LM) training in mental health as a key intervention, but little is known about employer training provisions.AimsTo explore the prevalence and characteristics of organizations that offer LM training in mental health.MethodsSecondary analysis of existing longitudinal anonymised organizational-level survey data derived from computer-assisted telephone interview surveys collected in four waves (2020:1900 firms, 2021:1551, 2022:1904, 2023:1902) in England, before, during and after a global pandemic.ResultsThe proportion of organizations offering LM training in mental health increased pre- to post-pandemic (2020:50%, 2023:59%) but 41% do not currently provide it. Logistic regression confirmed that LM training is more likely to be offered by large-sized enterprises, organizations with a larger proportion of employees who are younger (aged 25-49), female, disabled and from ethnic minority communities. Sector patterns were inconsistent, but in 2023, organizations from the 'Hospitality' and 'Business Services' sectors were more likely to provide LM training than other sectors.ConclusionsContinued efforts are needed to increase the proportion of employers offering LM training in mental health, particularly small- to medium-sized enterprises, and organizations with predominantly male, White and/or older workforces.