Abstract Background Research increasingly highlight post-migration factors for migrants’ mental health status. We investigated the association between participation in a health promotion program and changes in migrants’ mental health, and if socio-demographic factors and length of time in the new home country, Sweden, influenced a potential association. Methods A five-week health promotion program named ‘Hälsostöd’ [Health Support], led by community health workers, was offered to migrants, primarily asylum seekers and newly arrived immigrants (N = 202). The framework for the program was salutogenic psycho-education, which focused on health effects of migration experiences, lifestyle and health, and the health care system. Mental health was measured at the start and end of the program. We analysed this follow up by using the recommended clinical cut off (i.e. > 11 of maximum 36, with higher scores indicating possible mental illness) in the 12- item version of the General Health Questionnaire (GHQ12). Chi Square test was used to analyse statistical significance of changes, and multinomial logistic regression to analyse associations to sociodemographic factors and length of stay in Sweden. Results The number of participants scoring above the clinical cut off after participation in the program (N = 79, 39.1%) was lower compared to the corresponding number before participation (N = 111, 55.0%), Chi Square = 10.17,p < .001. The majority of the participants had no change 72.3 (N = 146), 21.8% (N = 44) had a positive change, yet 5.9% (N = 12) had a negative change, compared to before participation in the program. None of the investigated sociodemographic factors showed to significantly influence the association. Length of stay in Sweden was trending, with participants with longer stay being more likely to have possible mental illness. Conclusion We conclude that psycho-educative programs, similar to ‘Hälsostöd’, have potential for promoting asylum seekers’ and newly arrived immigrants’ mental health as the evaluation showed a considerable number of positive changes in participants. The result suggests the importance of offering immigrants health promotive programs in close connection with arrival to the new home country. Future research should clarify under what circumstances sociodemographic factors influence the effects of such programs.