Lewis made his Celtic debut in February 2011 and joined Kilmarnock on loan in January 2012 for a six-month loan spell. In August 2012, he joined Dundee on a season-long loan.
The defender has represented Scotland and under-17 and under-19 level. He made his Scotland youth international debut in a 3-1 win over Slovakia in 2008 in a UEFA European Under-17 Championship qualifier.
He made his Scotland Under-21 debut in a friendly match against Italy in April 2012.