The 39-year-old plead guilty to two counts of robbery as well as carrying a bladed article in Wigan on October 31, 2017.
He was sentenced at Bolton Crown Court on Friday. Alker will be eligible for parole on January 12, 2020.
The former hooker played more than 350 games for Salford City Reds between 1997 and 2010.
Alker, who won two caps for England, was also a coach at the Super League side, but left in 2011.
He captained the side for nearly a decade, but was stripped of the role in 2009 after a breach of club discipline during a training camp in the USA.