Nando's was founded in South Africa and now runs more than 400 sites across the UK
The chicken chain, known for its Portuguese-inspired Peri-Peri flavours despite having been founded in South Africa, said the problems were a result of "disruption" across the UK supply chain.
On social media, the company described the supply issues as a "bit of a 'mare" and asked customers to remain patient.
It also said that it would be sending 70 of its staff to help to sort the supply issues more rapidly.
The Daily Mail reported that almost 50 of the chain's restaurants had been closed due to the issues.
The firm, which operates more than 950 restaurants worldwide including more than 400 in the UK, told customers complaining on Twitter that closures were down to members of the teams "completing isolation periods".
Elsewhere, the firm's official Twitter account wrote: "The UK supply chain is having a bit of a 'mare right now. This is having a knock-on effect with some of our restaurants across England, Scotland and Wales. We are doing everything we can to get the PERi-PERi back where it belongs - on your plates."
A Nando's spokesperson added: "The UK food industry has been experiencing disruption across its supply chain in recent weeks due to staff shortages, and a number of our restaurants have been impacted.
"However, we can confirm that from today Nando's will be lending seventy of our brilliant team members to support our key suppliers - working in partnership to help get things moving again.
"We expect to see this having a positive impact on the affected restaurants very soon, so please bear with us whilst we do everything we can to get our famous PERi-PERi chicken back where it belongs - on your plates!"
Across Scotland many of the chain's locations have limited delivery options, with some also having reduced hours.
The Nando's in Glasgow's Westend and at Soar, XSite Braehead, are both fully closed. The restaurant at Edinburgh's Straiton Park is currently open for collection only.
Any customers hoping to eat at a Nando's are asked to check the company's website for up-to-date information on each of their location's opening hours.
The restaurant chain uses Avara, Moy Park and 2 Sisters Food Group to supply its stores with chicken, according to the Daily Mail.
Ranjit Singh Boparan, of the 2 Sisters Food Group, previously warned the so-called "pingdemic" was masking other issues.
Speaking in July, Boparan said that in the second half of 2021 "the operating environment has deteriorated so profoundly I can see no other outcome than major food shortages in the UK".
Warning that chicken supplies were at "crisis point", he said Brexit had reduced staff available to the sector significantly, with his 16,000-strong workforce facing a 15% shortage.
He said: "The critical labour issue alone means we walk a tightrope every week at the moment.
"We're just about coping, but I can see if no support is forthcoming - and urgently - from government, then shelves will be empty, food waste will rocket simply because it cannot be processed, or delivered, and the shortages we saw last year will be peanuts in comparison to what could come."
Comment: Last year brutal, rolling, lockdowns caused vast amounts of produce of all kinds to be dumped and left to rot because it couldn't be harvested, processed, delivered, and it couldn't be sold because various food outlets were locked down. This man-made and totally avoidable food supply catastrophe also meant that preserved foods were not processed and stored, and farmers were left with huge losses, causing many to go out of business, or at least to drastically cut back this year. In addition, there's years worth of crop failures and animal culls, and more recently port closures and various other transport issues due to continued lockdowns, but also cyberattack and extreme weather phenomena.