The main bus route serving Castledermot is J.J. Kavanagh & Sons route 736 providing a very limited number of daily services to Carlow, Waterford, Dublin and Dublin Airport inter alia. This service was drastically reduced in 2015 which has badly affected local commuters and community members seeking to visit hospitals in Kildare and Dublin. Visitors who wish to visit Castledermot outside of the small number of services that pass through the town must alight at slip road off the M9 for Carlow and avail of a taxi service into Castledermot. If you are elderly it is advised to stand in the long grass off the road to avoid traffic which can pass at speeds up to 140km P/H. South Kildare Community Transport operate a route from Castledermot to Athy twice a day each way Mondays to Fridays inclusive. Bus Éireann used to serve Castledermot frequently but the solitary route 7 Sunday evening journey at 19.15hrs to Dublin was withdrawn in 2015. Castledermot is also served by bus route 880 operated by Kildare Local Link on behalf of the National Transport Authority. There are several buses each day including Sunday linking the town to Carlow and Naas as well as villages such as Moone in the area.
Carlow railway station is approximately 11 kilometres distant. Athy railway station is around 14 kilometres distant.