"I didn't know what to do, whether to attack the basket or pull up, but I knew I was going to take a shot," said Miller, who also had nine rebounds and six assists.
Philadelphia coach Tony DiLeo challenged his team to make at least five 3s after he thought the Sixers were being tentative because they were the worst long-distance shooting team in the NBA.
The 76ers entered at 29.5 percent from long range but kept firing, going 8-of-15 from 3-point range against the Bucks.
"We hit our goal tonight," DiLeo said. "That's what we want. We want them to have the confidence, the freedom, the green light to shoot whenever they're open."
Trailing by eight with just more than 10 minutes to play, the Sixers started taking -- and making -- their shots from behind the arc. They finished 4-of-6 for the quarter, none bigger than Miller's 3 right after Luke Ridnour made it 104-103 with a 3-pointer of his own with 49 seconds to play.
"He's unbelievable," DiLeo said of Miller. "He sees things out on the court, he runs the team, he knows when to push it and when to pull it out."
Miller went down the floor and Redd barely reacted, looking for a pick and expecting a drive when Miller pulled up and answered with his own 3 to push the lead to 107-103.
"I think I surprised Michael a little bit because the scouting report is that I'm not going to shoot the 3-pointer. It's something I work on, but I don't usually take them," Miller said.
After Milwaukee's Richard Jefferson, who finished with 27 points, added a layup, Andre Iguodala made one of two free throws with 17 seconds to play and Charlie Bell missed an off-balance 3 with seconds to play that would've tied it.
"He got the ball and I wasn't sure what he was trying to do, but I wasn't going to bite on his pump fake," said former Bucks guard Royal Ivey, who often practiced against Bell last season and also hit two 3s to help spark the Sixers earlier in the quarter. "He went straight up but I held my ground and the ref saw there was no contact."
Iguodala grabbed his fifth rebound and made two more free throws to finish with 20 points and seal the victory, the Sixers' second on the road in their last seven tries.
"It was a great team victory and a great character victory for us," said DiLeo, whose team has won back-to-back games after beating Houston at home on Tuesday night -- and four straight over the Bucks.
Milwaukee coach Scott Skiles continues to be frustrated with his team's defensive effort, a major emphasis this season by the new coach that the previous two failed to fix.
"We've shot the ball well enough to stay in these games but with so many breakdowns we're having a hard time overcoming them," Skiles said. "The other night we picked up our defense the last five minutes and a switch went on for us. Tonight we couldn't get it to go on."
"I don't think the last few games we've played the type of defense that's allowed us to be where we want to be," he said.
Milwaukee lost for just the second time in nine home games. The Bucks again played without center Andrew Bogut, who missed his third straight game because of back spasms.
"You can't make excuses. They were playing without Elton Brand," Jefferson said. "The team that wins the most games when they're short-handed will be the team that is where they need to be at the end of the season."
There's no timetable for Bogut's return. Milwaukee is 1-2 in the last three games and 1-5 this season without him. ... Lou Williams scored 12 points and Thaddeus Young 10 for the Sixers. Milwaukee got 26 points from Charlie Villanueva, 18 in the second quarter, 20 from Redd and 11 from Ridnour. ... Milwaukee was 1-of-8 from 3-point range in the fourth quarter. ... In the first meeting on Dec. 17, Iguodala scored four points on 2-of-14 shooting, while Redd had six points on 2-of-13 shooting. Both players surpassed those point totals a little more than nine minutes into the first quarter.