They were accused of trying to trick a 20-year-old woman from Slovakia into having an abortion and arranging her marriage to a man facing deportation.
The Crown Prosecution Service (CPS) says new evidence had emerged "which seriously undermined the prosecution".
Last November, 13 people were arrested in Greater Manchester but none will face further action.
A CPS spokeswoman said four men and a woman were initially charged with immigration offences and "intentionally arranging or facilitating entry into the UK of a person with a view to their exploitation".
She added: "The CPS concluded that there is no longer sufficient evidence to generate a realistic prospect of conviction, therefore on 1 April 2015 the CPS formally offered no evidence in the case against all five defendants."
Charges have been dropped against Mohammed Ali, 40, and Hateji Yakuyb, 57, both of Ashfield Road, Rochdale; Anna Cicakova, 34, and Malik Ramzan, 27, both of Wesley Street, Failsworth; and Rehman Ghani, 39, of St Heliers Drive, Cheetham Hill.
Charges have been dropped against five people who were accused of trafficking a pregnant woman into the UK.