The roasting time for pork tenderloin is 20 to 25 minutes. Because pork tenderloin is a lean cut of meat, it can overcook easily, so the best way to determine when it is done cooking is to check for an internal temperature of 140 to 145 degrees Fahrenheit.
For best results and a juicy tenderloin, the oven should be preheated at 450 degrees Fahrenheit with the cooking pan to be used pre-warmed inside. When the oven is ready, the tenderloin should be roasted for 10 minutes, then flipped to ensure a golden crust all over. After being flipped, the oven temperature should be turned down to 400 F and the tenderloin roasted for another 10 to 15 minutes.