Alonso made his debut for Nicaragua in a March 2000 World Cup qualification match against El Salvador and has earned a total of 37 caps, scoring no goals. He has represented his country in 5 FIFA World Cup qualification matches and played at the 2001, 2003, 2005, 2007, 2009 UNCAF Nations Cups, as well as at the 2009 CONCACAF Gold Cup. He also has been national team captain.