Altuve led the majors in batting this year. He is listed at just 5-foot-6.
"As soon as I cross the white line, I feel the same size as everyone else,'' Altuve said.
This was the 10th time that a player homered three times in a postseason game. Babe Ruth did it twice.
Pablo Sandoval was the last player to hit three homers in a postseason game, doing it for San Francisco in the 2012 World Series opener against Detroit.
"I told him the last time I've seen [someone] hit three home runs in a game was Pablo Sandoval and I gave up two of them, so I'm glad there's somebody new that's done it,'' winning pitcher Justin Verlander said.
Altuve became the first Astros player to hit three homers in one game since 2007, when Carlos Lee did it in the regular season. He seemed as surprised as anyone that he was now in a category with the Sultan of Swat, Reggie Jackson and Albert Pujols.
"I hit one and I was like: `Wow,''' he said. "And the second one is like: 'Wow, what's going on here?'''
And his thoughts after the third?
"I got to wake up,'' he said, flashing a huge grin.
After he finished talking to outfielder George Springer following his third shot, Altuve's teammates goaded him into exiting the dugout for a curtain call. And as he tipped his hat to the crowd, one fan near the dugout held a sign that proclaimed in blue block letters: "That Kid Can Hit.''
Information from The Associated Press was used in this report.