Orkney Islands Council says the decision to look at the proposal by Scottish Sea Farms once more follows legal advice that councillors took their decision based on the wrong planning blueprint.
The application from the company, which is owned by Salmar AS and the Leroy Seafood Group of Norway, is for a fish farm in Gairsay Sound between the island of Wyre and the north east of the Orkney mainland.
Fishermen objected because of the impact on the grounds of scallop divers and creel fishermen. They say the decision by the council is "unprecedented".
When it was considered on March 26 the vote was tied four each and the deciding vote against was cast by the planning committee's vice chairman.
But since the meeting, council officials say further scrutiny of the terms for committee's decision found that the reasoning was based partly on planning policy from the 2004 Local Plan. That specifically related to land-based, not marine, fish farm developments. The council's planning jurisdiction for sea-based fish farms came into effect in 2007.
A council spokesman said as the application was for a marine fish farm, legal advice was sought from a specialist planning lawyer who recommended that the application should be referred back to the committee for a fresh determination.
The application will now be considered afresh by the committee on April 30.
Orkney Fishermen's Association Secretary Fiona Matheson said: "We are obviously frustrated by the re-run of this crucial meeting but heartened at the sense shown by the OIC council members in their original rejection of the site."