Continuity mistake: When Rose is looking through Jack's sketchbook when they are sitting on deck near the beginning of the movie, Rose's hair changes form shot to shot. From one angle it is very messy, with a lot of wind blowing it around. However, from the other angle her hair is perfectly styled into ringlets around the front, with little or no wind blowing at it.
Factual error: When the men are checking the store room for Rose and Jack, the men are using huge battery powered bright white flash lights that look like they're from Jurassic Park, which were not around in 1912. Back then they would have produced yellow light.
Continuity mistake: When Rose is trying to rescue Jack she spies a fire axe. Smashing all the glass out from the holder she grabs the axe and turns round. The next camera shot shows Rose standing in front of the case with almost all of its glass intact.
Deliberate mistake: In the scene at the start of the movie with the "authentic" piece of film, you can see a girl with a hat waving to the people at the ground. When the ship is leaving port in the film, she and others are in the same positions, only in reverse, because the first "authentic" shot is the same shot, only reversed.
Continuity mistake: In the early scene where Jack wins the tickets for the voyage, his hand-rolled cigarette is thin and almost done just before he shows his hand. About five seconds later, the cigarette is fatter and longer.
Continuity mistake: Right before dinner, Jack and Rose are talking to the Astors, and Molly comes up from behind them, asking Jack to escort her to dinner as well. In the next scene, when Cal calls back to Rose, Molly is still walking up to them.
Continuity mistake: When the ship is about to leave the dock, there's a lot of people saying goodbye to the ones that are going to leave the city. In the following shots, you can see Jack and his friends playing cards inside the pub. If you look through the window you won't see anyone. In the next shot, when Jack leaves the pub, the crowd is there again.
Visible crew/equipment: When Jack and Rose are running away from Cal to the first class dining room, if you look at the glass you can see a black screen, a light, and a crewman.
Factual error: When Rose, Jack and his friends come up to the boat deck while the ship is sinking, they ascend using the second class staircase and its exit on the deck. When Jack lets go of the door it is able to hit the side of the deckhouse. On the actual Titanic there were walls on the bow side of each door, which supported an overhang above the entrance. This is not included in many scenes in the movie.
Continuity mistake: Look closely at the location of Rose's beauty-mark the first time you see her at the dock. It is on the opposite side of her face during the rest of the movie.
Revealing mistake: When the ship tilts to a vertical position, you see people falling and hitting objects on the deck. In a close up of that, you can see that a black and bronze-topped capstan has wrinkles in it and bends when someone hits it.
Factual error: The lake that Jack told Rose he went ice fishing on when she was threatening to jump is Lake Wissota, a man-made lake in Wisconsin near Chippewa Falls (where Jack grew up). The lake was only filled with water in 1918 when a power company built a dam on the Chippewa River, six years after the Titanic sank.
Continuity mistake: When Jack and Rose are talking on the deck. Rose is explaining to Jack why she considered jumping. She stated that she felt that she was screaming at the top of her lungs and no one was listening. He looks at her ring and states that she'd sink straight to the bottom...yadda, yadda, yadda. If you watch that scene, pay attention to Rose's hair. One second, her hair in perfectly curled with bangs, then it is behind her ears. It alternates back and forth: bangs, no bangs, bangs, no bangs until she grabs his portfolio and they sit down on the chairs to look at his drawings.
Revealing mistake: When the ship is sinking, there is a shot of Victor Garber leaning against the wall in deep contemplation. The camera angle is very tilted and a few things slide off the shelf in front of him. Look carefully on the DVD and you'll see a wire coming out under his arm behind him pulling the china cup off the shelf.
Factual error: When the camera pulls back through the pub window to reveal the card players, if you look carefully in the background you will see a Steam Engine on the dock. Unfortunately the computer generated loco is clearly American as it has two domes, something NEVER seen on British locos. It also is shunting what looks like a carriage - again, this is also American. Carriages were rarely seen at docks, except if a train was connecting to a ship, and this was not common until the 1920s.
Factual error: The Master-at-Arms office, where Jack is handcuffed, was in actuality an inside cabin and had no portholes at all.
Revealing mistake: Many scenes used computer graphics to show the length of the ship. Passengers were also added walking on deck. The shadows for the passengers don't always match. Sometimes the angle of the sun distorts shadows. So the shadow of a woman's hat appears much larger than the actual one she's wearing, much like a person's shadow at sunset can appear to be that of a giant.
Visible crew/equipment: When Jack and Rose enter the flooding dining room as Cal is chasing them there is a light and some equipment that can be seen through the window.
Continuity mistake: Just as Titanic breaks apart, the compass platform (seen in front of the third funnel when the lights were still on) suddenly disappears. The water isn't even high enough to have reached its aft-most legs. The white projection on the deck that held the chandelier in the lounge is also gone, and the ventilator that sits on it is flush with the deck.