Cornwall Council said it had been awarded more than Â£30,000 in grants to enable "essential works to be carried out" on the Grade II-listed Huer's Hut on the Towan headland.
The hut dates from the 19th Century, when Newquay was still a village and part of the pilchard industry.
The works were expected to take four weeks to complete, the council said.
The council - which has a long-term lease on the building, and is responsible for its repair and maintenance - said it had formally appointed contractor Ryearch to carry out the works on the hut.
Such huts provided shelter for lookouts, known as huers, who alerted fishermen to passing pilchard shoals.
Although the current building dated back to the mid-19th Century, the known history of the site went back to the 14th Century and it may have been a hermitage, the council said.

Jim Cassell headed City's academy when Sturridge spent three seasons there.
England (2011-present): 4 caps, 0 goals
Bolton Wanderers (loan 2011): 12 Premier League appearances, 8 goals
Chelsea (2009-2013): 96 appearances in all competitions, 24 goals
Manchester City (2006-09): 32 appearances in all competitions, 6 goals
And he has been frustrated at Sturridge's lack of first-team appearances at both City and Chelsea.
"Hopefully Liverpool will get the best from Daniel as he has the potential to be a top-class international striker," Cassell told BBC Sport.
Cassell was City's academy director for 12 years, from 1997 to 2009, until he was given a new job heading up the club's international academies.
During his time in the role, Cassell brought through Micah Richards, Stephen Ireland, Michael Johnson and Joey Barton, and won the 2008 Youth Cup.
And he quickly identified Sturridge, who moved to Manchester City from Coventry City as a 13-year-old in 2003, as a huge talent who could go on to achieve success at the highest level.
"Daniel was exceptional, even as a 13-year-old," Cassell said, after Sturridge completed his move to Liverpool from Chelsea for an undisclosed fee on Wednesday.
"He had great pace, fantastic feet and magnificent vision. I couldn't speak too highly of him when he was with us.
"He trained hard, was respectful and always immaculately turned out - I thought he was great. We knew he could go on and achieve great things."
Sturridge played in the 2006 Youth Cup final against Liverpool, which City lost 3-2 on aggregate despite the striker scoring twice in the home leg.
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He was promoted to the first team squad in the 2006-7 season, but went on to make only 21 appearances for City, scoring five goals.
In July 2009 he moved to Chelsea and, although he got more first-team opportunities and won four caps for England, he was often played out wide and again failed to make a first-team place up front his own.
Cassell admits it has sometimes been hard to watch such a talent sitting on the sidelines.
"It's frustrating," he said. "In English football, we sometimes don't get the most out of our young players. The problem is enabling them to really establish themselves. They need that to really make it at international level.
"The English game needs to be patient with these young talents."

Butler, 24, joined the Iron for an undisclosed fee from National League South side Hemel Hempstead in June.
He kept two clean sheets in six appearances for the club, but was sent off in their defeat by Macclesfield.
Fellow keeper Sam Beasant joined the club last week after his release by Cambridge United and made his debut against Guiseley last Saturday.
Work is due to start later in the autumn to repair a historic building in Newquay.
[NEXT_CONCEPT]
The man who brought Daniel Sturridge through the ranks at Manchester City hopes to finally see the striker fulfil his potential at new club Liverpool.
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Braintree Town have agreed to release goalkeeper Jamie Butler just 72 days after he signed for the club.