The 20-year-old headed home a pin-point cross from Shane Lowry to seal victory for the Lions, stretching their unbeaten run to 10 games.
Jackett said: "It was a real quality goal that decided it - a fantastic ball from Shane and Chris was in the right place at the right time.
"Any win in the Championship is hard-earned and this was no exception.
"Millwall v Leeds games are always very passionate. We're pleased to come out on top against a side as big as Leeds."
Wood, who extended his loan from West Brom until January immediately after the game, has now scored seven goals in 12 games for the Lions.
Jackett added: "We've been pleased with Chris, he's worked hard in the group and if as a centre-forward you can get in the habit of popping up with a winner, that's great. We've been very pleased."