Introduction
Yellow September (YS) is a Brazilian suicide prevention campaign implemented in 2015, however, its effectiveness in reducing mortality is still unknown. 

Materials and Methods
This is an ecologically interrupted time series study that analyses the evolution of suicide rates in Brazil between 2011 and 2019 and its association with the implementation of YS at a national level. Data was provided by the Mortality Information System. A segmented interrupted series regression analysis was performed, using a generalized linear Poisson model, with correction for seasonal trends. 

Results
There was an increase in the annual rates of suicide deaths between 2011 and 2019, with 4.99 and 6.41 suicides per 100,000 inhabitants, respectively. The null hypothesis, that the YS did not change the historical trend of growth in suicides in Brazil after its implementation, was affirmed. However, there was an eventual significant increase of 6.2% in the risk of mortality in 2017 and of 8.6% in 2019.

Discussion
The results are consistent with the literature, which proposes that campaigns focused solely on publications through the media generate unsound findings regarding the effective reduction in the number of deaths by suicide. Conclusions: The lack of initiative in multisectoral actions may explain the failure of YS on changing deaths by suicide, therefore the development of new lines of action focused on training professionals and expanding the care network could make it an effective instrument in reducing mortality from suicide.