The For The Love Of Dogs presenter, 64, wrote a heartfelt tribute to Cilla, who passed away in 2015 aged 72.
The pair were very close pals, and both worked and holidayed together.
Taking to his Instagram account, Paul addressed his some 78,800 followers.
Known for his self-deprecating humour, he poked fun at himself in the picture of him standing next to Cilla.
And he paid a gushing tribute to his late friend, and lamented on how much he missed her.
"Today would've been Cilla's 77th birthday"
He wrote: "Today would’ve been Cilla’s 77th birthday. I don’t know where or when this photo was taken but it must’ve been a while ago as my hair is brown (obviously a dye job) and I’d say we were well up for another late night in Shadow Lounge.
"I still miss the fun we had and I loved working with her."
Paul's fans flooded his comments with sympathy and many remarked how much they adored Cilla too.
A singer, presenter and author - Cilla was a British entertainment icon whose career spanned across five decades.
One user wrote: "She was good fun and I'm glad to have met/worked with her. I'm gonna play her greatest hits CD while I'm gardening. I love the lines 'Our Nellie's working at the loom and she gets paid on Friday'".
"She was good fun"
Paul replied: "The best was the phone call ‘are we going out tonight or what?'"
Another user commented: "I grew up with Cilla and loved her on Surprise Surprise and Blind Date. She was a legend and lovely lady. She certainly gave me a lorra lorra laughs bless her."
A third posted: "Loved Cilla . Hope you're keeping well Paul x."
And a fourth commented: "The amount of time your shenanigans made me blurt out laughing is unreal. Your friendship was beautiful xx."
Paul has spoken many times about his devastation over Cilla's unexpected passing.
"I couldn't believe it"
Appearing on Loose Women just months after her death, he expressed his disbelief over her being gone.
He told the ITV panel: "I couldn't believe it when I got the phone call, the press rang me up to tell me, and that's always the worst way to find out.
"Even now I sort of think, 'Oh, she's either in Barbados or Spain'.
"We used to go clubbing, we'd go on holiday together, spoke to her all the time, and even now I think, 'I must ring Cilla and tell her that'."
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