Summary: Run-time monitoring is an important technique to detect erroneous run-time behaviors. Several techniques have been proposed to automatically generate monitors from specification languages to check temporal and real-time properties. However, monitoring of probabilistic properties still requires manual generation. To overcome this problem, we define a formal property specification language called Probabilistic Timed Property Sequence Chart (PTPSC). PTPSC is a probabilistic and timed extension of the existing scenario-based specification formalism Property Sequence Chart (PSC). We have defined a formal grammar-based syntax and have implemented a syntax-directed translator that can automatically generate a probabilistic monitor which combines timed B"uchi automata and a sequential statistical hypothesis test process. We validate the generated monitors with a set of experiments performed with our tool WS-PSC Monitor.