The 28-year-old striker was deemed surplus to requirements following the appointment of Paul Jewell at Portman Road and could be available for Argyle's game against MK Dons.
Fallon joined the Tractor Boys in November with a view to a permanent move and made six appearances, scoring one goal.
The New Zealand international became the first ever Plymouth player to represent his country at the World Cup at last summer's tournament in South Africa.
Source: PA
Source: PA