The men, aged 38, 34 and 30, were arrested on Monday at separate addresses. They remain in custody.
Police said they were aware of the woman's identity but would not name her until her next of kin were informed.
Her body was found near Delamere Terrace in Little Venice, west London, on Sunday.
An initial post-mortem test on the woman's body proved "inconclusive" and further tests are required, Met Police detectives have said.
Det Ch Insp Simon Ashwin said: "We now believe that the body, in a black suitcase, was placed in the Grand Union Canal at some point in the last two weeks.
"Whilst the body was recovered near to Little Venice it is highly likely that she entered the water further along the canal."
He said the force was "following a number of lines of inquiry" and it was conducting house-to-house enquiries as well as reviewing CCTV footage.
Three men have been arrested on suspicion of murder after a woman's body was found in a suitcase dumped in London's Grand Union Canal.