Banahan moved to Bath in the summer of 2006, after previously appearing for the London Irish Academy and was brought to the Recreation Ground as a lock.

He switched to wing where his powerful combination of size, strength and speed made him a potent weapon in the Bath United and Development sides, for whom he scored ten tries in fourteen games last season.

On 10 January 2018, it was announced by Bath that Banahan will be leaving after 12-year association to West Country rivals, Gloucester from the 2018–19 season.

He made his full England debut on 6 June 2009 in a comfortable win over Argentina at Old Trafford where he also scored a try and was named 'Man of the Match'.

[11] On 21 August 2023, Banahan was announced as attack coach for the Scotland national women's rugby union team.