The 85 year old was killed by two Islamist armed gunmen who entered the church in Saint-Etienne-du-Rouvray in Normandy.
Father Hamel was holding Mass for a small gathering of people when the two assailants entered and took four people hostage. Local police reported that the priest's throat was slit in the attack.
At the time, Pope Francis issued a statement condemning the "absurd violence" and said during a Mass in September that Father Hamel "is blessed now".
Since his death on July 26th 2016, Islamic leaders throughout France encouraged Muslims to attend mass as a sign of solidarity.
The Islamic State claimed responsibility for the attack, saying that the two gunmen who were shot dead by the police were "soldiers" retaliating against a US led coalition fighting the group in Iraq and Syria.
To commemorate the anniversary, the Diocese of Rouen held a special Mass at the church of Saint-Etienne-du-Rouvray, at the same hour as the Mass he was celebrating when killed.
Afterwards, the community erected a stone in memory of Father Hamel to promote peace and fraternity.
The event was celebrated by Archbishop Dominique Lebrun, attended by French President Emmanuel Macron, and broadcast throughout the country.