The Irish actor, who stars alongside Fiennes in fantasy sequel Wrath Of The Titans, said their similar looks tend to get them mixed up.
''I get mistaken for my pal Ralph Fiennes. I've been congratulated for my Hamlet on Broadway 14 years ago,'' he said.
''And he gets mistaken for me sometimes. We'd pass as brothers, you know.'' added the actor, who also stars in sci-fi epic Battleship alongside Rihanna and Taylor Kitsch.
Neeson, 59, recounted two memorable times when he was mistaken for the Oscar-nominated English actor, who has starred in the Harry Potter films as villain Lord Voldemort, Schindler's List and The English Patient.
''I was once down in Patagonia, Argentina, about five years ago fly-fishing, and this woman came up and said, 'Oh my God, Red Dragon! You were fantastic in that.' I didn't want to say, 'It's not me', so I said, 'Thanks very much','' he said.
''And then, once, my wife .125Natasha Richardson.375 and I were walking through the Plaza Athenee, this beautiful hotel in Paris, and this elderly couple got up and said, 'Excuse me, my husband and I are visiting from America'.
''The lady grabbed one of these beautiful tea service menus and said, 'Would you mind signing this for us?' I said, 'It would be my absolute pleasure'. And as I'm about to sign it, she said, 'We absolutely adored The English Patient'.
Neeson added: ''So I signed it 'With love, Ralph Fiennes'. I could not burst their bubble.''
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