Detectives are questioning a 41-year-old man from Melbourne suburb Coburg who is believed to be the same person wearing a blue hoodie seen in the last CCTV footage captured of Meagher, 29, on Brunswick Rd early on Saturday morning (Australian time).
Reports say police are building a murder case.
The man, being held at a police station on St Kilda Road, has not been charged.
The arrest came after new CCTV footage from an art store, 300m from where Irish immigrant Meagher was pictured walking past a fashion store, shows she could have been followed for as long as several hundred metres before going missing on her way home from a bar.
Victoria Police have only released the bridal store footage and have not commented on its contents, other than calling for anyone who was in the area on the night and has any information that could help their investigations to come forward.
Michael McKeon, Meagher’s uncle, has spoken to The Irish Independent about the distraught family’s “a living nightmare”.
“That is how most people would describe it, everything stops until you find the person, life is kind of numb,” Mr McKeon said.