Be my guest Definition 1 of 1Pro Tip 1/3Permission Granted Use 'be my guest' to give someone permission in a friendly and informal way. Looking for another cookie? Be my guest! Pro Tip 2/3Slight Sarcasm It can sound sarcastic if you say 'be my guest' when you doubt someone's ability or decision. You want to try fixing it yourself? Be my guest. Pro Tip 3/3Informal Settings 'Be my guest' is not usually used in formal situations; keep it for casual conversation. Can I change the TV channel? Be my guest.