Hi Mary,
Thank you so much for taking the time to read my article and send your question. Yes, the daypack can hold a puff jacket or vest. Sometimes the puffy jacket comes with its own little bag with a hanging cord. When I had a puffy jacket that did not come with its own little bag, I’ve squished it up and stuffed it into a gallon freezer bag and rolled it up to let out the air. Then seal it and unroll to have a totally flat jacket to put into your suitcase. I’ve used the jacket in its own bag with a carabiner to attach to my daypack, too. I have that pink daypack and it’s super convenient. Thank you again! Happy travels!