Merah, a self-proclaimed Al-Qaeda sympathiser, shot dead a rabbi, three Jewish schoolchildren and three French paratroopers before being killed in a police siege in the city on March 22nd, last year.
The 23-year-old French citizen with Algerian roots, who in 2011 received military training in Pakistan, wanted to avenge Palestinian children and punish France for sending troops to Afghanistan.
Questions have been asked about the failure of France's intelligence services to prevent Merah carrying out his deadly crimes, despite the fact he was known to them and they had monitored him at various stages.
At a memorial service in Toulouse on Sunday, Hollande vowed that the victims' families will receive the truth.
"Could this tragedy have been avoided? Did Merah act alone or was he a member of a larger network?" asked Hollande. "The families and the whole of France are owed these answers. I will guarantee they get them."
"The state must do everything to help shed light on these questions and we must know the shortcomings of the services involved."
French police doubt that Merah could have acted alone, but the only person charged with helping him so far is his brother Abdelkader who has denied the charges.
Last month, police arrested two men in connection with Merah's killing spree, and in early December a 38-year-old man and his girlfriend were arrested on suspicion of links to the attacks but both were later released without charge.
Hollande said he remains committed to the fight against "terrorism".
"The fight against terrorism is global... and allows for no easing off, no weakness and no negligence," Hollande told a crowd of around 1,500 people that had gathered for the service.
"Democracy is always more powerful than fanaticism," Hollande said.
The president also vowed to crackdown on anti-Semitism and insisted that the government will force social network sites like Twitter and Facebook to hand over the names of those who publish racist or anti-Semitic material.
In January, a French court ordered Twitter to disclose data in order to identify the perpetrators of anti-Semitic tweets. It followed a lawsuit taken by France's Union of Jewish Students . The union has complained however that since then, the law has not been enforced.