Meghan met staff and animals at Mayhew, in Kensal Green, north-west London.
The two-picture post shows the duchess at the rescue centre, and stroking a dog with a collar.
According to the post: “The Duchess of Sussex, having been proud patron of Mayhew since January 2019 and long understanding the connection between animal and community welfare, applauds the people at Mayhew for the vital work they do every day.”
It is not clear when the visit took place, but Meghan was in the UK with her husband, the Duke of Sussex, in the second week of January when they carried out a number of engagements following their Christmas break in Canada.
The couple have since returned to Canada, after announcing they would be stepping down as senior royals and will no longer receive public funds for royal duties.
Meghan, an advocate of adopting rescue dogs, chose animal welfare charity Mayhew as one of her first patronages.
She previously visited the shelter in January 2019, and was introduced to Maggie, a one-year-old Jack Russell who was up for adoption on the charity’s website.
The duchess picked up Maggie when she saw her shivering, and clutched her to her chest as she chatted to Mayhew staff, who told her about the charity’s projects in India and Afghanistan.
During their engagement interview in 2017, Harry revealed that the Queen’s corgis quickly took a shine to his future wife.
He said: “The corgis took to you straight away.
“I’ve spent the last 33 years being barked at; this one walks in, absolutely nothing…”
Describing the moment, Meghan said: “Just laying on my feet during tea, it was very sweet.”
And Harry added: “Just wagging tails and I was just like argh.”
Mayhew was founded in 1886 and today sees itself as an animal welfare social worker, keeping cats and dogs, whether family pets or companions for the homeless, safe and well alongside their owners, and supporting communities.
It has a pet refuge service, provides vet services for vulnerable owners, and has a team of animal welfare officers who work with local residents helping local communities.