Hooker Hartley missed last weekend's defeat to France in Paris with a calf problem but has trained this week and is now back available for selection.
Daly picked up a foot problem against Les Bleus, having missed the first three rounds with a combination of calf and ankle problems.
The British & Irish Lions man has also been given the nod, with assistant coach Paul Gustard confirming the pair would be available to face the Irish on Saturday.
It could be a special St Patrick's Day for Joe Schmidt's men as they aim for only their country's third Grand Slam at Twickenham but, having been in the same situation 12 months ago, Gustard says Eddie Jones' side are aiming to spoil the party.
"We are well aware of the situation we are in - we have lost the last two, and we are looking forward to this weekend," he told BBC Radio 5 live.