Williams was back giving the crowd a one-arm raised victory twirl after reaching a 10th Wimbledon final after her opponent swiped a lob behind the baseline.
This semi-final was billed as attack versus defence and it was the solid, reliable manner of Kerber that prevailed as she let an erratic Ostapenko, who was going for winners on nearly every shot, hand her a swathe of free points.
After winning the Australian and US Open titles and reaching the Wimbledon final two years ago, Kerber endured a significant slump in 2017.
Williams is set to face another German player in the final, 11th-seed Angelique Kerber, who also booked a spot in the decisive match beating Latvia's Jelena Ostapenko 6-3, 6-3 in her respective semifinal.More news: Arsenal Complete Signing of Teenage Lorient Midfielder Matteo Guendouzi on Long-Term Deal
"These are the matches I was working for as a young kid", Kerber said, "and to stand here again in the final at Wimbledon is great".
Serena Williams demonstrated that having a baby had not robbed her of any of her phenomenal tennis skills when she became the first mother in 38 years to reach the Wimbledon final, with a 6-2 6-4 demolition of Germany's Julia Goerges on Thursday. She then played the Miami Masters and lost in the first round before withdrawing from the French Open before a fourth-round match against Maria Sharapova with a pecotral muscle injury.
And the first Latvian woman to make the Wimbledon semi-finals was paying the price for more rash mistakes as the match slipped away.
Kerber looked anxious and Ostapenko had a point to close to within a game but she dumped a backhand return into net and then coughed up two more errors to hand Kerber victory. She missed the 2017 tournament as she was pregnant with her daughter Alexis Jr., who was born on September 1 of that year.More news: United States president Donald Trump visits UK, in pictures
But she can move level with Court on 24 Slams won if she beats Angelique Kerber on Saturday afternoon.
Goerges is the only one of the four semi-finalists still waiting to win her first Grand Slam title.
Ostapenko suddenly began to land some big blows, clawing back a couple of games and had a point to narrow the deficit to a single game as Kerber showed late nerves.More news: Donald Trump flies in to a rough reception