Home treatment has been proposed as an alternative to inpatient treatment for people with acute mental illnesses. Although such services have been successfully established in various countries, only moderate evidence is available to support their effectiveness. While randomized controlled designs are the gold standard to estimate causal treatment effects, their practical application is not always feasible. This case study provides insights into the considerations of choosing an appropriate research design for evaluating a newly implemented home treatment in the context of limited resources. The potential and prerequisites for conducting an observational study including a propensity score matching analysis are discussed along with the use of medical routine data in mental health care research.