Dicko impressed manager Roberto Martinez in the Latics' pre-season matches against Preston and Villarreal.
Signing on: Dicko joining Wigan
He was a free agent after being released by French club Strasbourg because of their financial problems.
Martinez said: 'Nouah is a young prospect who came to our attention through our scouting network and he has impressed us whilst on trial.
'The unfortunate situation regarding his former club Strasbourg has meant that he has become available on the market and we feel he has the potential to develop. I am delighted he has agreed to join us.'
Dicko added: 'I am so happy to join the club and to be given this chance. I need to keep working hard now and try and push for a regular place in the first-team squad.'
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