Mrs Bio, who has been at the forefront of campaigning against sexual abuse since her husband became president six years ago, wanted the signing of the bill to be a big occasion.
Since MPs passed the legislation a few weeks ago, it has not received much coverage locally.
At the ceremony, President Bio said that his “motivation and commitment to empowering women and girls is firmly rooted in my personal life journey”.
His eight-year-old daughter was amongst those who watched him sign the bill.
The 60-year-old president explained how he had lost his father at an early age and had been brought up by his mother and later his elder sister who “supported and encouraged me to pursue my dreams to the best of my ability”.
He acknowledged his wife’s commitment to championing women’s rights: “Together, we want to build an empowered Sierra Leone where women are given an even platform to reach their full potential. I have always believed that the future of Sierra Leone is female.”
Rights activists reacted favorably to the lawm, calling it a watershed moment.
On their X page, the US Bureau of African Affairs welcomed the passage of the bill saying the “significant milestone not only protects girls but promotes robust human rights protections”.