A source told The Sun newspaper: "It's early days but it's something that their management and label are excited about.
"It may be documentary footage mixed with a concert film, or it could even be a comedy caper in the style of old Monkees films.
"All options are open, though they're unlikely to get cracking on shooting it until next year."
Harry - who is famed for his tousled locks - is particularly excited at the thought of appearing in 3D.
He said: "The film could be exciting. My hair would be poking in your eye."
Insiders believe the movie could be as successful as Justin Bieber's 'Never Say Never' documentary film, which earned over $98 million at the box office following its release in February 2011.
The source added: "US film experts are speculating that the 1D film would be similar to Justin's movie and will be a big money-spinner for the boys."