The One Direction singer wrote on Twitter: "Happy birthday Mum. I love you x."
Johannah Deakin, who was a Doncaster midwife, died of leukaemia in December.
His debut solo single Just Hold On was released just days later, and he dedicated the track to her, performing an emotional rendition on The X Factor.
The 25-year-old, a former pupil at both Hall Cross School and Hayfield School, recently opened up about the heartbreak he suffered following Johannah's death
In an interview with the SiriusXM radio station, he said he had wanted to 'throw the towel in' but was spurred on by her advice that he had to 'keep going'.
Louis' sister Lottie, a beauty blogger, also paid tribute via Twitter. She shared a photo of her and her mum, accompanied by the message: "Happy birthday Mum miss you and love you forever."
Ms Deakin, who had seven children, was cared for at University College London Hospital before being moved to the Royal Hallamshire Hospital in Sheffield for the last few weeks of her life. She died on December 7 last year.
Singer Louis Tomlinson has paid tribute to his mother on what would have been her 44th birthday, months after her death.
The One Direction star's mother Johannah Deakin died in December after suffering from an aggressive form of leukaemia.
Tomlinson, 25, wrote to his 24.3 million Twitter followers on Saturday: "Happy birthday Mum. I love you x."
Following her death, the pop star released the song Just Hold On - his debut solo single - in her honour and he performed it on The X Factor just days later.
His sister Lottie, a beauty blogger, also posted her own tribute to her more than 2.5 million Twitter followers.
She shared a picture of herself and her mother, and wrote: "Happy birthday Mum miss you and love you forever."
Mother-of-seven Mrs Deakin had been cared for at University College London hospital since May before being moved to the Royal Hallamshire Hospital in Sheffield for the last few weeks of her life at the end of last year.
She died on December 7.