McCartan is from Tullylish, County Down. His father, also called James is regarded as one of the game's all-time greats and won three All-Ireland medals with Down in the 1960s. James' brothers Daniel and Eoin are current members of the Down team, while Charlie Pat also played for Down and Brian was the captain of the 1987 Down minor team that won the All-Ireland Minor Championship. He is Greg Blaney's cousin.
Playing career
Club
Inter-county
In 1987 McCartan helped the Down Minor team win both the Ulster Minor and All-Ireland Minor Football Championships. He was aged just 16. McCartan made his Down Senior debut in 1990. For his performances in the 1990 Championship he received an All Star award. He was the star player during the NFL in which Down was defeated by Meath in the final. In 1991 he won his first Ulster Championship medal, with Down beating Donegal in the decider. Down defeated Kerry in the All-Ireland semi-final, before beating Meath in the All-Ireland final. McCartan was named man of the match for his display in the final. The success was Down's first All-Ireland Senior Football Championship title since 1968. McCartan won a second Ulster Championship medal with Down in 1994 - overcoming Tyrone comfortably in the decider. Victories over Cork in the All-Ireland semi-final and Dublin in the final gave McCartan another All-Ireland Senior medal. For his performances that year he received another All Star. McCartan reached further Ulster finals with Down in 1996, 1999 and 2003, but the county were beaten on each occasion. He retired from inter-county football in 2003.
Province
McCartan also represented Ulster on many occasions, and won the Railway Cup four times with the province.
Since retiring McCartan has manager a number of teams. The first team he took charge of was Queen's University who he led to Sigerson Cup glory in 2007.
Down
On 11 September 2009, he was named manager of the Down senior football team. He led his team to the 2010 All-Ireland Senior Football Championship Final in his first season in charge but they lost to Cork. Down had a poor 2011 season only winning 3 Championship games. in 2012 James lead down to their first League Semi-final in 22 years where they played Cork it was a close game but cork won 2–17 to 1-12. McCartan lead Down to their first Ulster final since 2003 coming back from 0–11 to 0–02 to win by 1–14 to 1-13. In July 2014 McCartan stepped down as boss after 5 years in charge.