The Catalans hold a 3-0 advantage after their first leg win last week, yet the Argentinean is wary of the threat posed by his opposition’s strike-force.
"I don't know how Bayern will line up. But I expect a hungry Bayern team, right from the start,” he said. “They will try to score, we know how they play at home. But we are prepared for everything, nothing will surprise us. If we just defend they will come to us - now we are in the semi-final, it would be a mistake just to defend."
The 30-year-old says his side need to forget about their lead, and focus on securing a spot in this year’s Final.
"I think we need to forget that we are leading 3-0, we have to try to win this match,” he said. “We know that we are doing well in the league. If we try something different in this competition, we would be making a mistake.
"We are not excessively confident about what could happen in the game - they are going to try everything to progress.
"Tomorrow's game is really exciting for us. Playing in the Champions League final is a dream."
Mascherano was then asked about his compatriot Lionel Messi, who he feels is the best player “of all time”.
"I am a huge fan of Messi - I enjoy watching him,” he said. “You can’t compare him to anyone. For me he is the best player of all time."
Tuesday’s clash at the Allianz Arena is scheduled for 20:45.