Open throughout the year, daily 09:30 to 18:00 with last admission at 17:00 (the park website says 45 minutes before closing), closed 25, 26, 30 and 31 December; the park website adds that the centre closes every Monday and Tuesday from January to mid April. Free castle tours run Monday to Friday at 10:30, 12:00, 13:30, 15:00 and 16:00, subject to availability; ring 01 677 0095 to confirm. The walled garden opens daily 10:00 to 16:00. The visitor centre may close at short notice. Allow an hour.
The Biodiversity Centre at Knockmaroon, 2 km away by Knockmaroon Gate, is a separate seasonal site, open Wednesday to Sunday from April and closed for the winter. Tickets for the free Saturday tours of Áras an Uachtaráin are issued here from 09:30 on the day. Lift to the first floor, universal-access toilets, buggy storage, a free water refill station; the castle has narrow stairs and no lift. Café open 09:30 to 16:00 midweek in October. The playground (ages 4 to 12) opens 09:30 until an hour before sunset.
Dogs: Pet dogs on a lead around the visitor centre complex and demesne; not in the walled garden, the playground, the café or the toilets; the rule inside the exhibition and the castle is not published. The surrounding Phoenix Park, free at all hours: dogs under control, on a lead near the deer, on cycle lanes and near roads. In the surrounding park, signed restrictions near the deer at the rut (mid October to early November) and fawning (June and July).
Photo: Ashtown Castle, a tall stone tower house with a round-headed wooden door, behind low box hedges beside the Phoenix Park Visitor Centre. Cathalpeelo, CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:Dublin_-_Ashtown_Castle_-_20210918150557.jpg. Licence: https://creativecommons.org/licenses/by-sa/4.0. Resized and cropped for display; derivatives retain the source licence.