A two‐player planar target defense game where the intruder attempts to breach the circular region guarded by the defender in the presence of a fixed line segment obstacle is addressed. Based on prior research, the entire game was divided into three phases to address the partial information problem. Additionally, the impact of obstacles on the game outcome is thoroughly analyzed. In contrast to the scenario without obstacles, this paper presents redesigned strategies for both defender and intruder, accompanied by quantitative results illustrating the influence on the winning probability. Finally, illustrative examples are given to demonstrate the effect of the obstacle.