Seven-footer Lopez scored 21 points and his hot streak helped turn a two-point deficit into a 71-60 advantage as the Hornets cruised to the win.
"I was just in the right place at the right time," Lopez said. "(My team-mates), they all found me at the rim.
That's the way we're supposed to play."
It was just the second win in 11 games for New Orleans (5-11), who are rebuilding with a young roster and were without top overall draft pick Anthony Davis for the eighth straight game due to ankle problems.
Lopez spent his first four seasons in Phoenix before being traded to New Orleans in the off-season. He is off to a solid start and on Monday made eight of 10 shots from the field and all five of his free throws.
Ryan Anderson paced the scoring for New Orleans with 22 points, one of six Hornets to finish in double figures.
New Orleans grabbed a 10-point lead in the second quarter before the Bucks battled back to take a brief edge in the third.
Milwaukee were coming off a quality win against Boston on Saturday but could not find a similar effort to get them over the line on Monday as they were outscored 49-31 in the second half and shot just 38 percent for the game.
The Bucks were led by Brandon Jennings' 25 points but they have now lost six of their last eight games to fall out of first place in the Central standings.
"It seemed like we dribbled into crowds tonight and had trouble getting out of crowds," said Bucks coach Scott Skiles.
"When we start dribbling too much, we get in trouble."
Reserve Larry Sanders, who scored a career-high against the Celtics and notched a triple-double one game earlier, had seven blocks against the Hornets to go with eight points and seven rebounds.
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