[3] The only child of Eunice Sullivan, Andrew moved from his London home to the United States in 1996 where he attended St. Augustine Preparatory School, in Richland, New Jersey.

Sullivan took to his first season with the Wildcats in 1999–2000, on his debut playing with three rebounds and tough defense in seven minutes against Lafayette, and later the freshman converted his first career points with a 3-point shot from the top of the key in the first half against Fairleigh Dickinson.

Overall, it was a successful rookie season for the Englishman, in which another highlight unfolded when he made several plays in an 86–69 win over Notre Dame, ending the night with seven points and five rebounds in 14 minutes of activity.

[citation needed]He was the only Wildcat to start all 32 contests and connected on .529 of his field goal attempts, chalking up a 5.65 PPG average, or a combined total of 181 points throughout the season.

His key steal on Dayton's last offensive possession gave the Wildcats a chance to win on a final trip down the floor and his 28 minutes established a new career high as did his point total.

After just one season in the Netherlands, Sullivan returned to his homeland and immediately signed for leading British Basketball League team the Newcastle Eagles in 2004.

First claiming the BBL Trophy with a 71–51 win over the Leicester Riders, Sullivan himself contributing with a game high 18 points, as well as 11 rebounds, 4 assists and 3 steals, which earned him the MVP award.

The Eagles doubled their success with an 83–69 victory in the final of the BBL Cup against London Towers, with another 18 points, and also 2 blocked shots coming from the power forward.

In the four games that he did feature, Sullivan averaged 31 minutes-per-game, 5 rebounds-per-game and 18.25 points-per-game, with his tournament high coming against South Africa where he scored 23 points in a 95–53 win.

More recently, Andrew has featured in the newly founded Great Britain national team who competed in Eurobasket 2009 and whose aim is to push for a medal at the London 2012 Olympic games.

One of only two players, along with Nate Reinking, to remain from the inception of the Great Britain programme in 2006, Andrew has been the GB team's captain in recent years.