Atlanta finally found some offense after that, but the Rockets didn't slow down and had soon extended their lead to 60-40 after a pair of free throws by Harden with about two minutes left in the second quarter.
Harden made a 3-pointer just before halftime to leave Houston up 64-46.
Houston has won five straight over Atlanta, including a 109-102 win earlier this season when Harden had a career-high 45 points. He wasn't as dominant this time, but was still able to extend his career-long streak of games with 20-plus points to 13 games.
"Houston is a very hard team for us to match up with," Atlanta coach Larry Drew said. "We have a hard time defending this team."
Smith scored 17 with seven rebounds in his return after missing a game with a hip injury, and Al Horford had 18 points and 13 rebounds.
Delfino returned from a two-game absence with an illness to score a season-high 22 points, with six 3-pointers, and a career-high-tying eight assists. Asik added 11 points and 17 rebounds for the Rockets and Jeremy Lin added 16 points with eight assists.
Houston was up by eight with about two minutes left in the third quarter before the Rockets used a 9-0 run to extend the lead to 90-73. Delfino got it going with a 3-pointer and also had a layup in that span.
The Hawks used an 18-8 spurt in the first half of the third quarter to cut Houston's lead to 72-64. Atlanta shook off a second quarter where it shot just 29.2 percent by making three, 3-pointers to start the second half.
NOTES: Drew said that Devin Harris (sore left foot) and Anthony Morrow (right hip strain) aren't with the team and are both out until the team returns home on Saturday. He said he'd have an update on their status when they get back to Atlanta. ... The Hawks made 12 3-pointers for their franchise-record fourth consecutive game with at least 10 3-pointers. ... Smith had four blocks on Monday to move past Pau Gasol into 43rd place in NBA history with 1,365 blocks.