To simplify the expression \( \sqrt{6} + 2\sqrt{6} \), we can combine the like terms. Both terms involve \( \sqrt{6} \):
\[ \sqrt{6} + 2\sqrt{6} = 1\sqrt{6} + 2\sqrt{6} = (1 + 2)\sqrt{6} = 3\sqrt{6} \]
Therefore, the simplified expression is:
\[ 3\sqrt{6} \]