Chandler Parsons hit a tying 3-pointer from three steps behind the line at the regulation buzzer for the Rockets (45-37), who will face top-seeded Oklahoma City after losing four of six to end the regular season.
Harden scored 30 points and Parsons had 23 for the Rockets, who already knew they were back in the postseason after a three-year absence, but could have ended up in three seedings depending on Wednesday's results. Houston had a shot at the No. 6 spot before Golden State beat Portland earlier, but Los Angeles holds the tiebreaker on the Rockets.
Gasol had 17 points, 20 rebounds and 11 assists in his second triple-double in three games for the Lakers, who also held Houston well below its NBA-best average of 106.1 points per game. After a rocky regular season, the Lakers are heading into the playoffs with five straight wins, and eight in their last nine games.
The Lakers even won twice without Bryant, who tore his Achilles tendon last Friday and watched another game from his home in Orange County. Nash hasn't played in eight games with a hamstring injury, but the Lakers finished the regular season with a gritty comeback win despite Chandler's heroics.
Houston led for most of the night before the Lakers went ahead with 6½ minutes to play, but both teams struggled offensively in the final minutes before Parsons ended up alone with the ball near midcourt in the final seconds after a broken-play scramble. His desperate 3-pointer had almost no arch, but dropped in to force overtime.
The Lakers nursed a small lead over the Jazz (43-39) down the stretch of their tumultuous season, but Utah held the tiebreaker. The Jazz's 86-70 loss in Memphis clinched the Lakers' eighth straight postseason berth.