Police are searching for the perpetrators of the theft, which took place in broad daylight on one of the Mexican capital's most prestigious avenues, Avenida Reforma, CNN en Español reports.
The brazen heist is the latest development in a crime wave that has struck Mexico City in recent months as the security situation deteriorates across the country.
Two thieves entered the mint, taking a security guard's gun and throwing him to the ground before making off with 1,567 gold coins from the vault, which was left open, police told Reuters.
The "centenario" coins trade for 31,500 pesos ($1,610) each although their face value is just 50 pesos, according to Mexican bank Banorte. This means the booty is worth around $2.5 million in total.
Police told CNN en Español they are studying security camera footage provided by the mint, which shows the suspects in action.
Initial investigations revealed that security protocols were not followed and the guard and two other staff members who were working at the time have been taken in for questioning, according to a statement from Mexico City's Secretariat of Public Security.
Mexico's security situation has been worsening, with 33,341 homicides in 2018, according to a report released by Mexico's Secretariat of Security and Citizen Protection.
That is the highest number since the country began keeping records and compares with 28,866 homicides in 2017 -- an increase of more than 15%.
Many of the homicides are linked to violence among drug cartels fighting for control of territory.