The 58-year-old Bayern Munich coach sparred with the media in his pre-match news conference at the Santiago Bernabeu stadium, cracking jokes and delivering some killer one-liners before his side do battle with Mourinho's Inter Milan.
Beneath the banter was a serious message but Van Gaal, in contrast to his stuffy, self-important persona when he led Ajax Amsterdam to two Champions League finals in the mid-1990s, appeared at ease and far from overawed by the occasion.
He also gave an honest appraisal of Bayern's place in Europe's pecking order - even if they manage to lift the European Cup for the fifth time on Saturday.
"I think that Chelsea, Manchester United and Barcelona are the best teams in Europe but, nevertheless, we can win the title - we have shown our level. We were a little bit lucky against Manchester United but it was deserved I believe.
"Its always possible that a lower level club wins, that's sport, but I still believe Barcelona have played the best football this season in Europe.
"But little details can always decide a game, like when United's Rafael was sent off (against Bayern). But we are not at the top level yet, we can still improve."
Mourinho, the self-proclaimed 'Special One', worked for Van Gaal as an assistant coach at Barcelona in the late-1990s and the two men maintain a close friendship.
Asked if Mourinho was now the greatest manager of his generation, Van Gaal smiled knowingly and replied with the emphasis on the word "that":
"Well when you are talking that generation, you are right, he is 10 years younger than me of course...
"The first time I met him was with Bobby Robson and president Nunes at Barcelona and it was at this meeting I was told I was the new manager of the club.
"I presumed that Nunes had already told Bobby Robson but he had not told Mourinho - and he was so angry, really angry and he shouted - and I was impressed. He was already a special one for me then."
Van Gaal encouraged Mourinho's development and allowed him to coach a number of matches explaining: "He was an excellent co-trainer and deputy coach and he did an excellent job.
"I also let him coach matches for me, which was unusual, because he did have special qualities but little did I know that one day he would turn out to be such a great coach."
