The minor injuries unit at Tenby Cottage Hospital was closed as part of a shake-up of health services back in 2013 leading to public demonstrations.
Hywel Dda University Health Board hopes the new nurse-led walk-in service will open in July.
The board said the unit would provide "convenient access" for residents.
St John Ambulance Service will provide treatment for minor injuries over the Easter period.

"The attacker is trying to extort us money to make it stop," representatives of the company, which has 15 million users, said in a blog post.
"We refused to give in," they added.
On Tuesday, the popular online notes and web clippings service Evernote suffered a similar attack.
It is not yet known whether the two are linked, but Feedly and Evernote work closely together.
After coming under attack earlier on Wednesday, Feedly assured users their data was safe, and said it was working with its network provider to remove the threat.
On Tuesday, Evernote members were temporarily unable to synchronise their notes from one device to another while it continued.
The California-based company announced last month that it had more than 100 million users.
Distributed denial of service (DDoS) attacks are caused by what can be thousands of computers sending huge amounts of data to a target's servers in an effort to overwhelm them.
This sometimes involves hijacked PCs - whose owners may be unaware of their involvement - in what is known as a botnet.
This is not the first time Evernote has been compromised. In 2013 it said hackers had managed to access user names, email addresses and encrypted passwords.
However, it appears that the latest cyber-assault is more limited.
Spokeswoman Ronda Scott told the BBC that the cyber-assault, caused by an unknown perpetrator, began at 14:25 local time [22:25 BST] on Tuesday and had not yet ended.
"We continue to mitigate the effects of the attack, but have successfully returned Evernote to service," she added.
"As is the nature of DDoS attacks, there was no data loss, and no accounts were compromised."

The Insolvency Service said enough coal would be bought to keep the ovens alight as talks with "interested parties" continue about their future.
A spokesman said a further decision would be made next week.
The steelworks are with receivers after owners SSI UK went into liquidation, blaming a slump in global steel prices.
A statement from the Insolvency Service said: "A decision has been made to buy sufficient coal to keep the Redcar Coke Ovens going until the weekend, enabling the Official Receiver to continue discussions with interested parties about purchasing assets in working order.
"A decision about purchasing further coal to keep the ovens operational beyond the weekend will be taken at the end of this week."
The government has promised an Â£80m aid package to help the 1,700 workers who have lost their jobs.

Canon Jeremy Pemberton is a chaplain at Lincoln Hospital and has Permission to Officiate and leads occasional services in Nottinghamshire.
Gay marriage became legal in England and Wales last month but the move was not supported by the Church of England.
The Bishop of Lincoln said Mr Pemberton had been reminded of this policy.
Mr Pemberton, who describes himself as activist for LGBT equality in church and workplace, married his long-term partner on Saturday.
Supporters on social media predicted he would be the first of many gay clergy to wed.
The Bishop of Lincoln, the Right Reverend Christopher Lowson, said: "I am aware that a member of the clergy who works in the Diocese of Lincoln has married a partner of the same sex.
"The priest concerned wrote to me in advance to explain his intention and we had a subsequent meeting in which I explained the guidelines of the House of Bishops."
Commenting on Twitter last night, Mr Pemberton thanked well wishers but said "Nay-sayers we can talk another timeâ€¦maybe?"
Plans to open a new minor injuries unit in Pembrokeshire have got a step closer - four years after protests against the closure of the previous one.
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The news aggregator Feedly says it has come under a "distributed denial of service" attack from cyber criminals, which is preventing users from accessing its service.
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Coke ovens at the SSI Steelworks in Redcar will remain lit until at the least the weekend, the site's receivers have confirmed.
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An Anglican hospital chaplain has become what is believed to be the first member of the clergy in Britain to have a gay marriage.