Walmart doesn’t double coupons but they will price match the exact same item. Just take your ad with you and let them know at checkout the competitor’s ad price. (Some Walmart’s showcase competitor ads at the front of the store and already have it programmed into their system.)
Prices could vary by region. I also highly suggesting printing out the Walmart coupon policy and keeping it handy.
Looking for a grocery or a location I don’t cover, head over to The Frugal Map for a blog listing in your area!