Cut spaghetti squash in half either lengthwise or width wise (my preferred method). You can also leave whole, just be sure to cut a few slits in your squash to release pressure.
Place 1 cup cold water in pressure cooker. If using an 8 quart pressure cooker, use 1.5 cups of water. For a 10 quart instant pot use 2 cups water.
Place trivet of steamer basket in pressure cooker if using and place squash, cut side down on rack. By placing cut side down, you are helping to prevent condensation and water to collect inside the squash cavity.
Cook on HIGH pressure (select manual button or pressure cook button) and adjust to cook for 8 minutes for tender squash or 7 minutes for al dente squash. If you cook spaghetti squash whole, you will need to cook for 15 minutes on high pressure.
Remove squash from Instant Pot and use a fork to scrape into strands. Serve as desired.