気をつけて (Ki o tsukete) means "Take care" or "Be careful." You use this phrase to warn someone to be cautious, or to wish them safety when they are leaving, traveling, or doing something potentially risky. It conveys concern for their well-being.

相手に注意を促したり、安全を願ったりする時に使う言葉です。「気をつけて行ってらっしゃい」など。