The aim of this work was to determine the influence of different heat treatments on a PH 13-8 Mo maraging steel. In general, the heat treatment route of maraging steels consists of two stages. The first step, is solution annealing, which takes place in the austenite area, followed by precipitation hardening below the AC1 temperature. In this work, intercritical annealing was integrated into the conventional heat treatment to investigate its effect on the mechanical properties. It was of great interest to investigate if the additional intercritical annealing step supports the improvement of the toughness. In order to determine a heat treatment route that leads to ideal mechanical properties, different sequences for intercritical annealing in combination with solution annealing were carried out. To evaluate the heat-treated samples, the prior austenite grain size was investigated with an optical microscope, as well as X-ray diffraction analysis was performed to study the austenite content. The obtained microstructural findings were compared to the mechanical properties. This allowed an assessment of the effects of microstructural changes on hardness, toughness, and strength. The influence of the material condition were shown by using three different material states. For this purpose, heat treatments were carried out on untreated material, on a forged component, as well as on a component with deviating properties. It was determined that intercritical annealing has a positive influence on the toughness, of the PH13-8 Mo alloy. Furthermore, it was shown that the temperature of the intercritical annealing is a decisive factor to reach acceptable strength with simultaneously higher toughness. Additionally, the effect of different sequences of solution and intercritical annealing on the mechanical properties was shown. In future, the acquired knowledge could be helpful to control the mechanical properties of PH 13-8 Mo more precisely.