The bird first appeared at the front door of the Flower Box in Grantown on Spey two weeks ago.
Maria Norman, who owns the shop, said it started following her in each morning and would stay until she let it out in the afternoon.
However, the robin now stays in the shop all day and night rather than fly out the open door.
Ms Norman said: "He had been flying about outside and then started following me inside each morning.
"He would start to get agitated around half past three and I would open the door for him and he'd fly away.
"But now he doesn't fly out and stays in the shop and sings to the customers."
She added: "He has everything he needs in the shop - a tree, a bath and food."
The bird has been nicknamed Batman.
Birds have previously been regular visitors to shops, usually in search of food.
A robin sought shelter at an Aberdeen Co-operative during snowy weather in November 2010 and January the following year.
Customers at a supermarket cafe in Inverness took a shine to a robin that flew to and from tables in the run-up to Christmas in 2011.
People visiting the Tesco Extra store fed the bird crumbs.
In 2007, a seagull turned shoplifter by wandering into a shop and helping itself to crisps.
The bird walked into the RS McColl newsagents in Aberdeen when the door was open and made off with cheese Doritos.
The seagull, nicknamed Sam, became so popular that locals started paying for his crisps.
A robin has taken up residence in a festive tree decoration in a village flower shop.