Serena, playing her first tournament since a fourth-round loss at the Australian Open, had little trouble bypassing fifth-seeded Jelena Jankovic of Serbia 6-2, 6-2 in the quarterfinals.
The only blip in Williams' game came when she lost serve in a tentatively played fifth game in the first set.
"She was the better player tonight," Jankovic said. "Way better.
"I just played a bad match on my terms."
The only drama in the 76-minute match came in the final game with Jankovic serving.
The umpire, Kader Nouni of France, told Jankovic she was serving too fast and then too slow, when taking more than the 25 seconds allotted.
Williams was briefly brought into the fray when Jankovic made note that Williams often took more than the 25 seconds allowed to serve.
After the match, the players conversed at the net and both reported they left the court on good terms.
"I told her at the end, 'Look, I didn't mean anything. I'm sorry if I played slow,'" Williams said. "She was like, 'No, it was more like they say (I) play too fast and then too slow.' She said she couldn't get it right.
"I was like, 'Look, are we cool because I'm cool with you?'"
In that final game, Jankovic initially rebounded from love-40 before Williams won on a fourth match point with a scorching forehand passing shot.
Williams will play Alize Cornet of France in the semifinals. Cornet scored a 7-5, 6-3 win over Carla Suarez Navarro of Spain.
Venus Williams reached her fourth Dubai semifinal with a 6-3, 7-5 win over qualifier Flavia Pennetta of Italy.
Williams, who won this title in 2009 and 2010, had to serve for the match twice in the second set.
"She just keeps fighting," Williams said of Pennetta. "She stays relevant. That's what she does really well. I have to give her credit for that."
Serving at 5-4 in the second set, Williams missed out on a match point when Pennetta hit a forehand crosscourt winner to bring the score to deuce. Four points later and Pennetta broke serve to even the score at 5-5.
After Pennetta dropped serve in the 11th game Williams had a second chance to close out the match. Initially, Williams fell behind 0-40. On a second match point Pennetta popped a return long to concede the win.
Williams will play eighth-seeded Caroline Wozniacki, the 2011 Dubai champion, in Friday's semifinals.
Wozniacki had little trouble dispatching 27th-ranked Sorana Cirstea of Romania 6-1, 6-2.
"That was really pleasing, and I always know that Sorana can be a tricky opponent," Wozniacki said. "I felt like I served well and I put the pressure on her and played the way I wanted to play today."
Although not guaranteed, Venus Williams wasn't opposed to thinking ahead to the possibility of an all-Williams final on Saturday.
"It would be fantastic," Venus said. "But we both have to get there."Suggest a correction