Jancowicz, a Pole, made his last-four debut in a Grand Slam at the semifinal. He had previously beaten Murray at the Paris Masters in 2012.
But Murray was able to keep him back this time, even after losing the first set 6-7. He finished the following three sets 6-4, 6-4 and 6-3.
Jancowicz was a bit of a wild card in the tournament after a series of upsets in the first and second rounds. The 22-year-old was not the favorite to win, but was expected to put up a good fight against Murray and keep the win from being a given.
"For somebody who has got that much power, at 6-foot-8 with a monster of a serve, a big forehand and decent movement, he is always going to be a danger," Pat Cash said.
"He has beaten Murray convincingly before. Murray may have been a little bit off and thinking about the ATP World Tour finals a week later, but a win is a win and it will be at the back of Murray's mind."
Murray managed to pull it through, though, even with a move from Center Court due to rain.
Murray will face No. 1 Djokovic on Sunday after the Serbian came through a five-set match against Juan Martin del Potro in the longest men's semifinal in Wimbledon history. The match will be the fourth time the two have met in a final.
Djokovic is still the favorite, even though Murray won his semifinal more handily. The only time the two have met on grass was in the Olympics semifinals. Murray won in straight sets.