Is it okay for a preschooler to wet his pants once in a while?

Doesn't really sound like he is truly trained. Just because a child knows how to use the toilet doesn't mean they are "potty trained" per say. Some kids stay in a pull up thru the night up until age 5. I wouldn't expect him to hold it thru the night just yet. Are there any stressors maybe that are causing this? As far as during the day.You should try rewards. Try putting up a picture of a toy he would really like. Put a sticker on for each day he doesn't pee his pants. Then maybe after 7 days or so go to the store and buy him the toy. This is a reward system we used with my nephew and it seems to be working. He is 4. For each "naughty" thing he does we take a sticker off.