Career
Armstrong"s first club was Newcastle United, where in October 1993 he came up from their youth team He left in June 1994 having not played for them, and signed with Stockport County for £50,000. In 200 games for them, he scored 62 goals.
In February 1998 he joined Middlesbrough for £1.6m.
He stayed until 2000, when in March he joined Huddersfield Town for three months on loan. In December 2000 he joined Ipswich Town for £500,000.
Armstrong described the goal as "probably the most important of my career, as long as we get a result out there (In the return leg)". Despite Armstrong scoring another goal in the return leg from the penalty spot, Ipswich were knocked out with an aggregate score of 4–2.
From December 2003 until March 2004 he was on loan to Bradford City, scoring once against Norwich City, and in September 2004 he joined Darlington on a free transfer.
He left Darlington in June 2005, to join Rushden & Diamonds. After a spell on loan at Doncaster Rovers, he re-signed for Darlington in August 2006 to join the club on a second spell, before leaving them again at the end of the 2006-2007 season. He scored once in his second spell at Darlington, against Hereford.
He signed for Newcastle Blue Star in the UniBond Division One North before quitting days after receiving a red card against Gateshead.